Author name code: usoskin
ADS astronomy entries on 2022-09-14
author:"Usoskin, Ilya G."
------------------------------------------------------------------------
Title: Extreme solar events
Authors: Cliver, Edward W.; Schrijver, Carolus J.; Shibata, Kazunari;
Usoskin, Ilya G.
Bibcode: 2022LRSP...19....2C
Altcode: 2022arXiv220509265C
We trace the evolution of research on extreme solar and
solar-terrestrial events from the 1859 Carrington event to the rapid
development of the last twenty years. Our focus is on the largest
observed/inferred/theoretical cases of sunspot groups, flares on the
Sun and Sun-like stars, coronal mass ejections, solar proton events,
and geomagnetic storms. The reviewed studies are based on modern
observations, historical or long-term data including the auroral and
cosmogenic radionuclide record, and Kepler observations of Sun-like
stars. We compile a table of 100- and 1000-year events based on
occurrence frequency distributions for the space weather phenomena
listed above. Questions considered include the Sun-like nature of
superflare stars and the existence of impactful but unpredictable solar
"black swans" and extreme "dragon king" solar phenomena that can involve
different physics from that operating in events which are merely large.
Title: Solar Energetic-Particle Ground-Level Enhancements and the
Solar Cycle
Authors: Owens, Mathew J.; Barnard, Luke A.; Pope, Benjamin J. S.;
Lockwood, Mike; Usoskin, Ilya; Asvestari, Eleanna
Bibcode: 2022SoPh..297..105O
Altcode: 2022arXiv220712787O
Severe geomagnetic storms appear to be ordered by the solar cycle in
a number of ways. They occur more frequently close to solar maximum
and the declining phase, are more common in larger solar cycles,
and show different patterns of occurrence in odd- and even-numbered
solar cycles. Our knowledge of the most extreme space-weather events,
however, comes from spikes in cosmogenic-isotope (14C,
10Be, and 36Cl) records that are attributed
to significantly larger solar energetic-particle (SEP) events than
have been observed during the space age. Despite both storms and
SEPs being driven by solar-eruptive phenomena, the event-by-event
correspondence between extreme storms and extreme SEPs is low. Thus,
it should not be assumed a priori that the solar-cycle patterns found
for storms also hold for SEPs and the cosmogenic-isotope events. In
this study, we investigate the solar-cycle trends in the timing and
magnitude of the 67 SEP ground-level enhancements (GLEs) recorded
by neutron monitors since the mid-1950s. Using a number of models of
GLE-occurrence probability, we show that GLEs are around a factor of
four more likely around solar maximum than around solar minimum, and
that they preferentially occur earlier in even-numbered solar cycles
than in odd-numbered cycles. There are insufficient data to conclusively
determine whether larger solar cycles produce more GLEs. Implications
for putative space-weather events in the cosmogenic-isotope records
are discussed. We find that GLEs tend to cluster within a few tens
of days, likely due to particularly productive individual active
regions, and with approximately 11-year separations, owing to the
solar-cycle ordering. However, these timescales would not explain any
cosmogenic-isotope spikes requiring multiple extreme SEP events over
consecutive years.
Title: Solar cyclic activity over the last millennium
reconstructedfrom annual 14C data (Corrigendum)
Authors: Usoskin, I. G.; Solanki, S. K.; Krivova, N.; Hofer, B.;
Kovaltsov, G. A.; Wacker, L.; Brehm, N.; Kromer, B.
Bibcode: 2022A&A...664C...3U
Altcode:
No abstract at ADS
Title: Long-term forcing of Sun's coronal field, open flux and
cosmic ray modulation potential during grand minima, maxima and
regular activity phases by the solar dynamo mechanism
Authors: Dash, Soumyaranjan; Nandy, Dibyendu; Usoskin, Ilya
Bibcode: 2022arXiv220812103D
Altcode:
Magnetic fields generated in the Sun's interior by the solar dynamo
mechanism drive solar activity over a range of time-scales. While
space-based observations of the Sun's corona exist only for few decades,
direct sunspot observations exist for a few centuries, solar open flux
and cosmic ray flux variations can be reconstructed through studies of
cosmogenic isotopes over thousands of years. While such reconstructions
indicate the presence of extreme solar activity fluctuations in
the past, causal links between millennia scale dynamo activity,
consequent coronal field, solar open flux and cosmic ray modulation
remain elusive. By utilizing a stochastically forced solar dynamo model
we perform long-term simulations to illuminate how the dynamo generated
magnetic fields govern the structure of the solar corona and the state
of the heliosphere -- as indicated by variations in the open flux
and cosmic ray modulation potential. We establish differences in the
nature of the large-scale structuring of the solar corona during grand
maximum, minimum, and regular solar activity phases and simulate how the
open flux and cosmic ray modulation potential varies over time scales
encompassing these different phases of solar activity. We demonstrate
that the power spectrum of simulated and reconstructed solar open flux
are consistent with each other. Our study provides the theoretical
basis for interpreting long-term solar cycle variability based on
reconstructions relying on cosmogenic isotopes and connects solar
internal variations to the forcing of the state of the heliosphere.
Title: Rapid Auroral Wandering During the Laschamp Event
Authors: Mukhopadhyay, Agnit; Usoskin, Ilya; Liemohn, Michael;
Panovska, Sanja; Brenner, Austin; Garcia-Sage, Katherine; Welling,
Daniel; Ganushkina, Natalia
Bibcode: 2022cosp...44.1573M
Altcode:
41 thousand years ago, the Laschamp geomagnetic excursion caused Earth's
magnetic field to drastically diminish to $\sim$4% of the modern
dipole moment and altered its dipole-dominated structure. While the
impact of this geomagnetic event on environmental factors and human
lifestyle has been contemplated to be linked with modifications in the
geospace environment, no concerted investigation has been conducted
to study this until recently. In particular, the structure of the
magnetosphere during such an event was unconstrained. We present an
initial investigation of the global space environment and related
plasma environments during several phases of the Laschamp event using
an advanced multi-model approach. We use recent paleomagnetic field
models of this event to study the paleomagnetosphere going beyond a
simple dipole approximation but consider a realistic geomagnetic field
configuration. The field is used within the global magnetohydrodynamic
model BATS-R-US to simulate the magnetosphere during discrete epochs
spanning the peak of the event. Since solar conditions have remained
fairly constant over the last $\sim$100k years, modern estimates of
the solar wind were used to drive the model. Finally, plasma pressure
and currents generated by BATS-R-US at their inner boundary are used
to compute auroral fluxes using a stand-alone version of the MAGNIT
model, an adiabatic kinetic model of the aurora. Our results show that
changes in the geomagnetic field, both in strength and direction, have
profound effects on the space environment and the ensuing auroral
pattern. Magnetopause distances during the deepest phase of the
excursion match previous predictions, while high-resolution mapping of
magnetic fields allow close examination of magnetospheric structure
for non-dipolar configurations. Temporal progression of the event
also exhibits rapid locomotion of the auroral region over ~250 years
along with the movement of the geomagnetic poles. Our estimates suggest
that the aurora extended to low latitudes, with the center of the oval
located at near-equatorial latitudes during the peak of the event. While
the study does not find evidence of any link between geomagnetic
variability and habitability conditions, geographic locations of the
auroral oval coincide with early human activity in Eurasia and Oceania.
Title: Application of a neutron monitor data analysis for
quantification of cosmic-ray induced terrestrial effects
Authors: Mishev, Alexander; Usoskin, Ilya
Bibcode: 2022cosp...44.1061M
Altcode:
The studies of cosmic rays (CRs) performed with the worldwide NM
network provide key information about various processes, such as
production and acceleration of energetic particles at the Sun and the
interplanetary medium, interactions of galactic cosmic rays (GCRs) with
magnetic fields in the heliosphere i.e. probing the electromagnetic and
plasma conditions of the heliosphere. The introduction of an NM as a
continuous recorder of CR intensity resulted from the design by John
Simpson. During the International Geophysical Year (IGY) 1957-1958,
a 12-counter neutron monitor was designed. Lately, the design of NM
was optimized resulting in an increase of the counting rates, appearing
the second generation of NMs known as NM64, nowadays used as a standard
detector. Besides, a specific class of solar energetic particles (SEPs),
namely those registered at the ground by neutron monitors, that is,
ground-level enhancements (GLEs), are conveniently studied using NM
data. GLE events are numbered consecutively, starting from the first
event that was detected in 1942. The most recent event was No. 73 in
October 2021. An important topic in the field of space physics is
related to the quantification of CR effects on atmospheric physics
and chemistry as well as space weather. For this purpose is necessary
to possess precise information of SEP spectra. This can be achieved
based on NM data analysis. Here we demonstrate the capabilities of
the verified method for the determination of SEP spectra and pitch
angle distributions in their dynamical development throughout GLE
events. Subsequently, on the basis of the derived spectra, we assess
the ion production rate in the atmosphere and exposure to radiation
at flight altitudes, thus quantifying important cosmic-ray induced
terrestrial effects.
Title: Characteristics of the First Ground Level Enhancement (GLE)
of Solar Cycle 25 on 28 October 2021
Authors: Papaioannou, Athanasios; Usoskin, Ilya; Gieseler, Jan; Herbst,
Konstantin; Kühl, Patrick; Rouillard, Alexis; Mishev, Alexander;
Wimmer-Schweingruber, Robert; Vainio, Rami; Anastasiadis, Anastasios;
Kouloumvakos, Athanasios
Bibcode: 2022cosp...44.1064P
Altcode:
We present an overview of the first ground-level enhancement (GLE)
event of solar cycle 25, recorded on 28 October 2021 (GLE73), based
on the available neutron monitor (NM) network observations and on data
from near-Earth spacecraft (GOES, SOHO, SolO). The maximum increase was
$\sim$7.3% for DOMC (Dome C NM at Concordia station) and 5.4% for SOPO
(South Pole) conventional NMs located on the Antarctic plateau. Bare
(lead-free) NMs at the same sites detected a higher response (14.0%
for DOMB and 6.6% for SOPB). The Fort Smith (FSMT) NM shows the earliest
increase among the high-latitude NMs, indicating a moderate anisotropy
in the first phase of the GLE event. The maximum rigidity of accelerated
protons did not exceed 2.4 GV. We estimated the solar release time (SRT)
of $\geq$1 GV protons into open magnetic field lines at $\sim$15:40
UT. In-situ proton observations from near-Earth spacecraft were
combined with the detection of a solar flare in soft X-rays (SXRs),
a coronal mass ejection (CME), radio bursts and extreme ultraviolet
(EUV) observations to identify the solar origin of the GLE. Around the
$\geq$1 GV proton SRT the CME-driven shock was located at a height of
$\sim$2.33 Rs. The timing of the EUV wave evolution towards the field
lines magnetically connected to Earth seem to be in good agreement
with the inferred release time of $\geq$1 GV protons.
Title: Spectral and Anisotropy Characteristics of the Solar Protons
during Ground Level Enhancement (GLE) # 73 on 28 October 2021 derived
with Neutron Monitor data
Authors: Mishev, Alexander; Usoskin, Ilya; Koldobskiy, Sergey;
Kocharov, Leon; Larsen, Nicholas
Bibcode: 2022cosp...44.1075M
Altcode:
The first ground-level enhancement of the current solar cycle 25
occurred on 28 October 2021. It was observed by several space-borne
and ground-based instruments, specifically neutron monitors. A moderate
count-rate increase over the galactic-cosmic ray background was observed
by high-altitude polar stations on the South Pole and Concordia stations
at the Antarctic plateau. Most of the neutron monitors registered
only a marginal increase. Here, using de-trended records, employing
verified by direct space-borne measurements method we derived the
rigidity spectra and angular distribution of incoming solar protons
for the GLE #73. We employed the newly computed and parameterized
neutron-monitor yield function. The rigidity spectra and anisotropy of
the solar protons were obtained in their dynamical evolution throughout
the event. Quantification of acceleration mechanism is discussed.
Title: Reconstructions of solar activity and variability from
cosmogenic isotope data
Authors: Krivova, Natalie; Usoskin, Ilya
Bibcode: 2022cosp...44.1046K
Altcode:
Our knowledge about the activity and variability of the Sun on the
millennial time scale relies on cosmogenic isotope data. Modulated by
the solar open magnetic field, the fluctuating flux of the energetic
cosmic ray particles in the vicinity of Earth leads to the formation
of varying amounts of the radionuclides in the atmosphere. These
radionuclides are naturally stored in terrestrial archives for millennia
and can be measured in laboratories nowadays. In combination with
appropriate models, such data then allow us to go back in time and
understand how the Sun behaved in the past. We will review the latest
progress in understanding and reconstruction of the solar activity
over the last millennia.
Title: Analysis of diurnal cosmic-ray variations as observed by
polar NMs
Authors: Gil, Agnieszka; Usoskin, Ilya; Poluianov, Stepan; Mishev,
Alexander
Bibcode: 2022cosp...44.1067G
Altcode:
Galactic cosmic rays (GCRs) show a low local anisotropy perceived as
a diurnal variability of neutron-monitor (NM) count rates. The NMs
have different abilities of observations of the GCR diurnal variation,
because their asymptotic directions are spatially diverse at a large
extent. We demonstrate that there is one NM at Dome C (DOMC) which
does not observe diurnal variability. Compared to other polar NMs,
for which the diurnal variation amplitudes span between 0.16 to 0.4%,
it is very small (0.03%) for DOMC. It is due to the narrow asymptotic
cone of the DOMC NM, directed practically in the polar direction
with geographic latitude over 75 degrees south. Hence, DOMC NM is the
uniquely located NM, which accepts cosmic rays from the off-equatorial
and off-ecliptic plane. This is of special interest for comprehensive
studies of cosmic-ray transport in the Earth vicinity, particularly
for anisotropic solar energetic particle events.
Title: Long-Term Solar Variability and Solar Cycle Predictions:
Current State of Understanding
Authors: Nandi, Dibyendu; Usoskin, Ilya; Pevtsov, Alexei
Bibcode: 2022cosp...44.3520N
Altcode:
The Sun's activity varies over timescales ranging from the very short
to the very long. Long-term solar activity variations impact the
Earth's atmosphere and climate and have implications for space mission
planning and life-time estimates. This variability across different
scales is driven by solar magnetic fields which originate in the deep
convection zone, emerge through the surface and evolve. Understanding
the physical basis for long-term variability over decadal scales and
longer is important for developing predictive models for sunspot cycle
which is an outstanding challenge. Concurrently, exploring the basis
of fluctuations that lead to extreme episodes such as grand maxima in
solar activity remains an important exercise with no clear indication
that such episodes are predictable. We shall review here the current
state of our understanding of long-term solar variability, and identify
challenges that are expected to spur future developments in this field.
Title: High-Resolution Spectral and Anisotropy Characteristics of
Solar Protons During the GLE N∘73 on 28 October 2021
Derived with Neutron-Monitor Data Analysis
Authors: Mishev, Alexander L.; Kocharov, Leon G.; Koldobskiy, Sergey
A.; Larsen, Nicholas; Riihonen, Esa; Vainio, Rami; Usoskin, Ilya G.
Bibcode: 2022SoPh..297...88M
Altcode:
The first ground-level enhancement of the current Solar Cycle 25
occurred on 28 October 2021. It was observed by several space-borne
and ground-based instruments, specifically neutron monitors. A
moderate count-rate increase over the background was observed by
high-altitude polar stations on the South Pole and Dome C stations at
the Antarctic plateau. Most of the neutron monitors registered only
marginal count-rate increases. Using detrended records and employing
a method verified by direct space-borne measurements, we derive the
rigidity spectra and angular distributions of the incoming solar
protons in the vicinity of Earth. For the analysis, we employed a
newly computed and parameterized neutron-monitor yield function. The
rigidity spectra and anisotropy of solar protons were obtained in their
time evolution throughout the event. A comparison with the Solar and
Heliospheric Observatory/Energetic and Relativistic Nuclei and Electron
(SOHO/ENRE) experiment data is also performed. We briefly discuss the
results derived from our analysis.
Title: Properties of Daily Helium Fluxes
Authors: Aguilar, M.; Cavasonza, L. Ali; Ambrosi, G.; Arruda, L.;
Attig, N.; Barao, F.; Barrin, L.; Bartoloni, A.; Başeǧmez-du Pree,
S.; Battiston, R.; Behlmann, M.; Berdugo, J.; Bertucci, B.; Bindi,
V.; Bollweg, K.; Borgia, B.; Boschini, M. J.; Bourquin, M.; Bueno,
E. F.; Burger, J.; Burger, W. J.; Burmeister, S.; Cai, X. D.; Capell,
M.; Casaus, J.; Castellini, G.; Cervelli, F.; Chang, Y. H.; Chen,
G. M.; Chen, G. R.; Chen, H. S.; Chen, Y.; Cheng, L.; Chou, H. Y.;
Chouridou, S.; Choutko, V.; Chung, C. H.; Clark, C.; Coignet, G.;
Consolandi, C.; Contin, A.; Corti, C.; Cui, Z.; Dadzie, K.; Dass,
A.; Delgado, C.; Della Torre, S.; Demirköz, M. B.; Derome, L.; Di
Falco, S.; Di Felice, V.; Díaz, C.; Dimiccoli, F.; von Doetinchem,
P.; Dong, F.; Donnini, F.; Duranti, M.; Egorov, A.; Eline, A.; Feng,
J.; Fiandrini, E.; Fisher, P.; Formato, V.; Freeman, C.; Gámez,
C.; García-López, R. J.; Gargiulo, C.; Gast, H.; Gervasi, M.;
Giovacchini, F.; Gómez-Coral, D. M.; Gong, J.; Goy, C.; Grabski, V.;
Grandi, D.; Graziani, M.; Haino, S.; Han, K. C.; Hashmani, R. K.;
He, Z. H.; Heber, B.; Hsieh, T. H.; Hu, J. Y.; Incagli, M.; Jang,
W. Y.; Jia, Yi; Jinchi, H.; Karagöz, G.; Khiali, B.; Kim, G. N.;
Kirn, Th.; Konyushikhin, M.; Kounina, O.; Kounine, A.; Koutsenko, V.;
Krasnopevtsev, D.; Kuhlman, A.; Kulemzin, A.; La Vacca, G.; Laudi, E.;
Laurenti, G.; Lazzizzera, I.; Lee, H. T.; Lee, S. C.; Li, H. L.; Li,
J. Q.; Li, M.; Li, Q.; Li, Q. Y.; Li, S.; Li, S. L.; Li, J. H.; Li,
Z. H.; Liang, J.; Liang, M. J.; Light, C.; Lin, C. H.; Lippert, T.;
Liu, J. H.; Lu, S. Q.; Lu, Y. S.; Luebelsmeyer, K.; Luo, J. Z.; Luo,
Xi; Machate, F.; Mañá, C.; Marín, J.; Marquardt, J.; Martin, T.;
Martínez, G.; Masi, N.; Maurin, D.; Medvedeva, T.; Menchaca-Rocha,
A.; Meng, Q.; Mikhailov, V. V.; Molero, M.; Mott, P.; Mussolin, L.;
Negrete, J.; Nikonov, N.; Nozzoli, F.; Ocampo-Peleteiro, J.; Oliva,
A.; Orcinha, M.; Palermo, M.; Palmonari, F.; Paniccia, M.; Pashnin,
A.; Pauluzzi, M.; Pensotti, S.; Plyaskin, V.; Pohl, M.; Poluianov, S.;
Qin, X.; Qu, Z. Y.; Quadrani, L.; Rancoita, P. G.; Rapin, D.; Conde,
A. Reina; Robyn, E.; Rosier-Lees, S.; Rozhkov, A.; Rozza, D.; Sagdeev,
R.; Schael, S.; von Dratzig, A. Schultz; Schwering, G.; Seo, E. S.;
Shan, B. S.; Siedenburg, T.; Song, J. W.; Song, X. J.; Sonnabend, R.;
Strigari, L.; Su, T.; Sun, Q.; Sun, Z. T.; Tacconi, M.; Tang, X. W.;
Tang, Z. C.; Tian, J.; Ting, Samuel C. C.; Ting, S. M.; Tomassetti,
N.; Torsti, J.; Urban, T.; Usoskin, I.; Vagelli, V.; Vainio, R.;
Valencia-Otero, M.; Valente, E.; Valtonen, E.; Vázquez Acosta, M.;
Vecchi, M.; Velasco, M.; Vialle, J. P.; Wang, C. X.; Wang, L.; Wang,
L. Q.; Wang, N. H.; Wang, Q. L.; Wang, S.; Wang, X.; Wang, Yu; Wang,
Z. M.; Wei, J.; Weng, Z. L.; Wu, H.; Xiong, R. Q.; Xu, W.; Yan, Q.;
Yang, Y.; Yashin, I. I.; Yi, H.; Yu, Y. M.; Yu, Z. Q.; Zannoni, M.;
Zhang, C.; Zhang, F.; Zhang, F. Z.; Zhang, J. H.; Zhang, Z.; Zhao,
F.; Zheng, C.; Zheng, Z. M.; Zhuang, H. L.; Zhukov, V.; Zichichi,
A.; Zuccon, P.; AMS Collaboration
Bibcode: 2022PhRvL.128w1102A
Altcode:
We present the precision measurement of 2824 daily helium fluxes in
cosmic rays from May 20, 2011 to October 29, 2019 in the rigidity
interval from 1.71 to 100 GV based on 7.6 ×108 helium
nuclei collected with the Alpha Magnetic Spectrometer (AMS) aboard
the International Space Station. The helium flux and the helium to
proton flux ratio exhibit variations on multiple timescales. In nearly
all the time intervals from 2014 to 2018, we observed recurrent helium
flux variations with a period of 27 days. Shorter periods of 9 days and
13.5 days are observed in 2016. The strength of all three periodicities
changes with time and rigidity. In the entire time period, we found that
below ∼7 GV the helium flux exhibits larger time variations than the
proton flux, and above ∼7 GV the helium to proton flux ratio is time
independent. Remarkably, below 2.4 GV a hysteresis between the helium
to proton flux ratio and the helium flux was observed at greater than
the 7 σ level. This shows that at low rigidity the modulation of the
helium to proton flux ratio is different before and after the solar
maximum in 2014.
Title: The first ground-level enhancement of solar cycle 25 on 28
October 2021
Authors: Papaioannou, A.; Kouloumvakos, A.; Mishev, A.; Vainio, R.;
Usoskin, I.; Herbst, K.; Rouillard, A. P.; Anastasiadis, A.; Gieseler,
J.; Wimmer-Schweingruber, R.; Kühl, P.
Bibcode: 2022A&A...660L...5P
Altcode: 2022arXiv220207927P
Aims: The first relativistic solar proton event of solar
cycle 25 was detected on 28 October 2021 by neutron monitors (NMs)
on the ground and particle detectors on board spacecraft in near-Earth
space. This is the first ground-level enhancement (GLE) of the current
cycle. A detailed reconstruction of the NM response together with the
identification of the solar eruption that generated these particles is
investigated based on in situ and remote-sensing measurements.
Methods: In situ proton observations from a few MeV to ∼500 MeV
were combined with the detection of a solar flare in soft X-rays,
a coronal mass ejection, radio bursts, and extreme ultraviolet (EUV)
observations to identify the solar origin of the GLE. Timing analysis
was performed, and a relation to the solar sources was outlined.
Results: GLE73 reached a maximum particle rigidity of ∼2.4 GV
and is associated with type III, type II, and type IV radio bursts
and an EUV wave. A diversity of time profiles recorded by NMs was
observed. This points to the event having an anisotropic nature. The
peak flux at E > 10 MeV was only ∼30 pfu and remained at this level
for several days. The release time of ≥1 GV particles was found to
be ∼15:40 UT. GLE73 had a moderately hard rigidity spectrum at very
high energies (γ ∼ 5.5). Comparison of GLE73 to previous GLEs with
similar solar drivers is performed. Movies are available at https://www.aanda.org
Title: Performance of the current and extended global NM network
for solar particle registration and analysis
Authors: Mishev, A.; Usoskin, I.
Bibcode: 2022icrc.confE1315M
Altcode: 2022PoS...395E1315M
No abstract at ADS
Title: New reconstruction of the event-integrated spectra for
GLE events
Authors: Koldobskiy, S.; Raukunen, O.; Vainio, R.; Kovaltsov, G.;
Usoskin, I.
Bibcode: 2022icrc.confE1273K
Altcode: 2022PoS...395E1273K
No abstract at ADS
Title: High-multiplicity neutron events registered by NEMESIS
experiment
Authors: Kasztelan, M.; Enqvist, T.; Jędrzejczak, K.; Joutsenvaara,
J.; Kotavaara, O.; Kuusiniemi, P.; Loo, K. K.; Orzechowski, J.;
Puputti, J.; Sobkow, A.; Słupecki, M.; Szabelski, J.; Usoskin, I.;
Trzaska, W. H.; Ward, T. E.
Bibcode: 2022icrc.confE.497K
Altcode: 2022PoS...395E.497K
No abstract at ADS
Title: Strongest directly observed Solar Proton Event of 23-Feb-1956:
Revised reference for the cosmogenic-isotope method
Authors: Usoskin, I.; Koldobskiy, S.; Kovaltsov, G.; Sukhodolov, T.;
Mishev, A.; Mironova, I.
Bibcode: 2022icrc.confE1319U
Altcode: 2022PoS...395E1319U
No abstract at ADS
Title: Pulse height-length analysis of data from neutron monitors
DOMC/DOMB with a new data acquisition system
Authors: Similä, M.; Poluianov, S.; Usoskin, I.; Mishev, A.;
Kovaltsov, G.; Strauss, D. T.
Bibcode: 2022icrc.confE1237S
Altcode: 2022PoS...395E1237S
No abstract at ADS
Title: Application of the verified neutron monitor yield function
for GLE analysis
Authors: Mishev, A.; Usoskin, I.; Koldobskiy, S.; Kovaltsov, G.;
Kocharov, L.
Bibcode: 2022icrc.confE1236M
Altcode: 2022PoS...395E1236M
No abstract at ADS
Title: New NEMESIS Results
Authors: Trzaska, W. H.; Enqvist, T.; Jędrzejczak, K.; Joutsenvaara,
J.; Kasztelan, M.; Kotavaara, O.; Kuusiniemi, P.; Loo, K.; Orzechowski,
J.; Puputti, J.; Sobkow, A.; Słupecki, M.; Szabelski, J.; Usoskin,
I.; Ward, T.
Bibcode: 2022icrc.confE.514T
Altcode: 2022PoS...395E.514T
No abstract at ADS
Title: A major update of the International GLE Database: Correction
for the variable GCR background
Authors: Usoskin, I.; Koldobskiy, S.; Gil, A.; Kovaltsov, G.; Usoskina,
I.; Willamo, T.; Ibragimov, A.
Bibcode: 2022icrc.confE1241U
Altcode: 2022PoS...395E1241U
No abstract at ADS
Title: Role of heavier-than-proton nuclei in neutron monitor response
Authors: Koldobskiy, S.; Kovaltsov, G.; Usoskin, I.
Bibcode: 2022icrc.confE1284K
Altcode: 2022PoS...395E1284K
No abstract at ADS
Title: New neutron monitor altitude-dependent yield function and
its application to an analysis of neutron-monitor data
Authors: Mishev, A.; Koldobskiy, S.; Kovaltsov, G.; Gil, A.;
Usoskin, I.
Bibcode: 2022icrc.confE1247M
Altcode: 2022PoS...395E1247M
No abstract at ADS
Title: Quality survey of Neutron Monitor data sources for 1951-2019
Authors: Väisänen, P.; Usoskin, I.; Mursula, K.
Bibcode: 2022icrc.confE1244V
Altcode: 2022PoS...395E1244V
No abstract at ADS
Title: Halloween GLEs on October-November 2003, spectra and angular
distribution: Revised results
Authors: Mishev, A.; Usoskin, I.; Kocharov, L.
Bibcode: 2022icrc.confE1261M
Altcode: 2022PoS...395E1261M
No abstract at ADS
Title: Tree-rings reveal two strong solar proton events in 7176 and
5259 BCE
Authors: Brehm, Nicolas; Christl, Marcus; Knowles, Timothy D. J.;
Casanova, Emmanuelle; Evershed, Richard P.; Adolphi, Florian;
Muscheler, Raimund; Synal, Hans-Arno; Mekhaldi, Florian; Paleari,
Chiara I.; Leuschner, Hanns-Hubert; Bayliss, Alex; Nicolussi, Kurt;
Pichler, Thomas; Schlüchter, Christian; Pearson, Charlotte L.;
Salzer, Matthew W.; Fonti, Patrick; Nievergelt, Daniel; Hantemirov,
Rashit; Brown, David M.; Usoskin, Ilya; Wacker, Lukas
Bibcode: 2022NatCo..13.1196B
Altcode:
The Sun sporadically produces eruptive events leading to intense
fluxes of solar energetic particles (SEPs) that dramatically disrupt
the near-Earth radiation environment. Such events have been directly
studied for the last decades but little is known about the occurrence
and magnitude of rare, extreme SEP events. Presently, a few events
that produced measurable signals in cosmogenic radionuclides such
as 14C, 10Be and 36Cl have been
found. Analyzing annual 14C concentrations in tree-rings
from Switzerland, Germany, Ireland, Russia, and the USA we discovered
two spikes in atmospheric 14C occurring in 7176 and 5259
BCE. The ~2% increases of atmospheric 14C recorded for
both events exceed all previously known 14C peaks but after
correction for the geomagnetic field, they are comparable to the largest
event of this type discovered so far at 775 CE. These strong events
serve as accurate time markers for the synchronization with floating
tree-ring and ice core records and provide critical information on
the previous occurrence of extreme solar events which may threaten
modern infrastructure.
Title: Time Lag Between Cosmic-Ray and Solar Variability: Sunspot
Numbers and Open Solar Magnetic Flux
Authors: Koldobskiy, Sergey A.; Kähkönen, Riikka; Hofer, Bernhard;
Krivova, Natalie A.; Kovaltsov, Gennady A.; Usoskin, Ilya G.
Bibcode: 2022SoPh..297...38K
Altcode:
Solar magnetic activity drives the dominant 11-year cyclic variability
of different space environmental indices, but they can be delayed
with respect to the original variations due to the different physical
processes involved. Here, we analyzed the pairwise time lags between
three global solar and heliospheric indices: sunspot numbers (SSN),
representing the solar surface magnetic activity, the open solar flux
(OSF), representing the heliospheric magnetic variability, and the
galactic cosmic-ray (GCR) intensity near Earth, using the standard
cross-correlation and the more detailed wavelet-coherence methods. All
the three indices appear highly coherent at a timescale longer than
a few years with persistent high coherence at the timescale of the
11-year solar cycle. The GCR variability is delayed with respect to
the inverted SSN by about eight 27-day Bartels rotations on average,
but the delay varies greatly with the 22-year cycle, being shorter or
longer around positive A + or negative A − solar polarity epochs,
respectively. The 22-year cyclicity of the time lag is determined by
the global heliospheric drift effects, in agreement with theoretical
models. The OSF lags by about one year behind SSN, and is likely
determined by a combination of the short lifetime of active regions and
a longer (≈3 years) transport time of the surface magnetic field to
the poles. GCRs covary nearly in antiphase with the OSF, also depicting
a strong 22-year cycle in the delay, confirming that the OSF is a
good index of the heliospheric modulation of GCRs. This provides an
important observational constraint for solar and heliospheric physics.
Title: Effective Energy of Cosmogenic Isotope (10Be,
14C and 36Cl) Production by Solar Energetic
Particles and Galactic Cosmic Rays
Authors: Koldobskiy, Sergey; Usoskin, Ilya; Kovaltsov, Gennady A.
Bibcode: 2022JGRA..12729919K
Altcode:
Cosmogenic isotopes 14C, 10Be and 36Cl
measured in datable natural archives provide the only known quantitative
proxy for cosmic-ray (CR) and solar-activity variability before the
era of direct measurements. Studies of relations between the measured
isotope concentrations and CR variability require complicated modeling
including the isotope production and transport in the terrestrial
system. Here we propose a rough "effective energy" method to make
quick estimates of the CR variability directly from the cosmogenic
data using an approximate linear scaling between the measured isotope
concentrations and the energy-integrated flux of CR above the effective
energy. The method is based on the thoroughly computed effective yield
function presented here. A simple way to account for the variable
geomagnetic field is also provided. The method was developed for
both solar energetic particles (SEPs) and galactic cosmic ray (GCR)
variability and is shown to provide a robust result within 20% and 1%
accuracy, respectively, without an assumption of the specific spectral
shape. Applications of the effective-energy method to the known extreme
SEP events and the secular GCR variability are discussed. The new
method provides a simple and quick tool to assess the CR variability
in the past. On the other hand, it does not supersede the full detailed
modeling required for precise results.
Title: Application of CCM SOCOL-AERv2-BE to cosmogenic beryllium
isotopes: description and validation for polar regions
Authors: Golubenko, Kseniia; Rozanov, Eugene; Kovaltsov, Gennady;
Leppänen, Ari-Pekka; Sukhodolov, Timofei; Usoskin, Ilya
Bibcode: 2021GMD....14.7605G
Altcode:
The short-living cosmogenic isotope 7Be, which is produced
by cosmic rays in the atmosphere, is often used as a tracer for
atmospheric dynamics, with precise and high-resolution measurements
covering the recent decades. The long-living isotope 10Be,
as measured in polar ice cores with an annual resolution, is a proxy
for long-term cosmic-ray variability, whose signal can, however,
be distorted by atmospheric transport and deposition that need to be
properly modeled to be accounted for. While transport of 7Be
can be modeled with high accuracy using the known meteorological
fields, atmospheric transport of 10Be was typically modeled
using case-study-specific simulations or simplified box models based
on parameterizations. Thus, there is a need for a realistic model
able to simulate atmospheric transport and deposition of beryllium
with a focus on polar regions and (inter)annual timescales that is
potentially able to operate in a self-consistent mode without the
prescribed meteorology. Since measurements of 10Be are
extremely laborious and hence scarce, it is difficult to compare
model results directly with measurement data. On the other hand,
the two beryllium isotopes are believed to have similar transport
and deposition properties, being different only in production and
lifetime, and thus the results of 7Be transport can be
generally applied to 10Be. Here we present a new model,
called CCM SOCOL-AERv2-BE, to trace isotopes of 7Be and
10Be in the atmosphere based on the chemistry-climate model
(CCM) SOCOL (SOlar Climate Ozone Links), which has been improved by
including modules for the production, deposition, and transport of
7Be and 10Be. Production of the isotopes was
modeled for both galactic and solar cosmic rays by applying the CRAC
(Cosmic Ray Atmospheric Cascade) model. Transport of 7Be was
modeled without additional gravitational settling due to the submicron
size of the background aerosol particles. An interactive deposition
scheme was applied including both wet and dry deposition. Modeling was
performed using a full nudging to the meteorological fields for the
period of 2002-2008 with a spin-up period of 1996-2001. The modeled
concentrations of 7Be in near-ground air were compared with
the measured ones at a weekly time resolution in four nearly antipodal
high-latitude locations: two in the Northern (Finland and Canada) and
two in the Southern (Chile and the Kerguelen Islands) Hemisphere. The
model results agree with the measurements in the absolute level within
error bars, implying that the production, decay, and lateral deposition
are correctly reproduced. The model also correctly reproduces the
temporal variability of 7Be concentrations on annual and
sub-annual scales, including the presence and absence of the annual
cycle in the Northern and Southern Hemisphere, respectively. We
also modeled the production and transport of 7Be for a
major solar energetic particle event (SPE) on 20 January 2005, which
appears insufficient to produce a measurable signal but may serve as
a reference event for historically known extreme SPEs. Thus, a new
full 3D time-dependent model, based on CCM SOCOL, of 7Be
and 10Be atmospheric production, transport, and deposition
has been developed. Comparison with real data on the 7Be
concentration in the near-ground air validates the model and its
accuracy.
Title: Ground Level Enhancement Events: Interplanetary Protons versus
Protons Interacting at the Sun.
Authors: Kocharov, Leon; Usoskin, Ilya; Mishev, Alexander
Bibcode: 2021AGUFMSH51B..03K
Altcode:
We compare results of the solar high-energy proton detection with
the neutron monitor network in Ground Level Enhancement (GLE) events
and the data of pion-decay gamma-ray emission produced by high-energy
protons interacting at the Sun. Observational data support the idea of a
common origin of the GLE-producing protons and the protons interacting
at the Sun to produce sustained gamma-ray emission. Then we discuss
capabilities of the CME bow-shock acceleration models to explain the
observational data and argue for the flare and CME synergy in production
of high-energy protons in the long duration events.
Title: Periodicities in the Daily Proton Fluxes from 2011 to 2019
Measured by the Alpha Magnetic Spectrometer on the International
Space Station from 1 to 100 GV
Authors: Aguilar, M.; Cavasonza, L. Ali; Ambrosi, G.; Arruda, L.;
Attig, N.; Barao, F.; Barrin, L.; Bartoloni, A.; Başeǧmez-du Pree,
S.; Battiston, R.; Behlmann, M.; Beranek, B.; Berdugo, J.; Bertucci,
B.; Bindi, V.; Bollweg, K.; Borgia, B.; Boschini, M. J.; Bourquin, M.;
Bueno, E. F.; Burger, J.; Burger, W. J.; Burmeister, S.; Cai, X. D.;
Capell, M.; Casaus, J.; Castellini, G.; Cervelli, F.; Chang, Y. H.;
Chen, G. M.; Chen, G. R.; Chen, H. S.; Chen, Y.; Cheng, L.; Chou,
H. Y.; Chouridou, S.; Choutko, V.; Chung, C. H.; Clark, C.; Coignet,
G.; Consolandi, C.; Contin, A.; Corti, C.; Cui, Z.; Dadzie, K.; Dass,
A.; Delgado, C.; Della Torre, S.; Demirköz, M. B.; Derome, L.; Di
Falco, S.; Di Felice, V.; Díaz, C.; Dimiccoli, F.; von Doetinchem,
P.; Dong, F.; Donnini, F.; Duranti, M.; Egorov, A.; Eline, A.; Feng,
J.; Fiandrini, E.; Fisher, P.; Formato, V.; Freeman, C.; Gámez,
C.; García-López, R. J.; Gargiulo, C.; Gast, H.; Gervasi, M.;
Giovacchini, F.; Gómez-Coral, D. M.; Gong, J.; Goy, C.; Grabski, V.;
Grandi, D.; Graziani, M.; Haino, S.; Han, K. C.; Hashmani, R. K.;
He, Z. H.; Heber, B.; Hsieh, T. H.; Hu, J. Y.; Incagli, M.; Jang,
W. Y.; Jia, Yi; Jinchi, H.; Karagöz, G.; Khiali, B.; Kim, G. N.;
Kirn, Th.; Konyushikhin, M.; Kounina, O.; Kounine, A.; Koutsenko, V.;
Krasnopevtsev, D.; Kuhlman, A.; Kulemzin, A.; La Vacca, G.; Laudi, E.;
Laurenti, G.; Lazzizzera, I.; Lebedev, A.; Lee, H. T.; Lee, S. C.;
Li, J. Q.; Li, M.; Li, Q.; Li, S.; Li, J. H.; Li, Z. H.; Liang, J.;
Light, C.; Lin, C. H.; Lippert, T.; Liu, J. H.; Liu, Z.; Lu, S. Q.;
Lu, Y. S.; Luebelsmeyer, K.; Luo, J. Z.; Luo, Xi; Machate, F.; Mañá,
C.; Marín, J.; Marquardt, J.; Martin, T.; Martínez, G.; Masi, N.;
Maurin, D.; Medvedeva, T.; Menchaca-Rocha, A.; Meng, Q.; Mikhailov,
V. V.; Molero, M.; Mott, P.; Mussolin, L.; Negrete, J.; Nikonov,
N.; Nozzoli, F.; Oliva, A.; Orcinha, M.; Palermo, M.; Palmonari,
F.; Paniccia, M.; Pashnin, A.; Pauluzzi, M.; Pensotti, S.; Phan,
H. D.; Plyaskin, V.; Pohl, M.; Poluianov, S.; Qin, X.; Qu, Z. Y.;
Quadrani, L.; Rancoita, P. G.; Rapin, D.; Conde, A. Reina; Robyn,
E.; Rosier-Lees, S.; Rozhkov, A.; Rozza, D.; Sagdeev, R.; Schael,
S.; von Dratzig, A. Schultz; Schwering, G.; Seo, E. S.; Shakfa, Z.;
Shan, B. S.; Siedenburg, T.; Solano, C.; Song, J. W.; Song, X. J.;
Sonnabend, R.; Strigari, L.; Su, T.; Sun, Q.; Sun, Z. T.; Tacconi,
M.; Tang, X. W.; Tang, Z. C.; Tian, J.; Ting, Samuel C. C.; Ting,
S. M.; Tomassetti, N.; Torsti, J.; Urban, T.; Usoskin, I.; Vagelli,
V.; Vainio, R.; Valencia-Otero, M.; Valente, E.; Valtonen, E.;
Vázquez Acosta, M.; Vecchi, M.; Velasco, M.; Vialle, J. P.; Wang,
C. X.; Wang, L.; Wang, L. Q.; Wang, N. H.; Wang, Q. L.; Wang, S.;
Wang, X.; Wang, Yu; Wang, Z. M.; Wei, J.; Weng, Z. L.; Wu, H.; Xiong,
R. Q.; Xu, W.; Yan, Q.; Yang, Y.; Yashin, I. I.; Yi, H.; Yu, Y. M.;
Yu, Z. Q.; Zannoni, M.; Zhang, C.; Zhang, F.; Zhang, F. Z.; Zhang,
J. H.; Zhang, Z.; Zhao, F.; Zheng, C.; Zheng, Z. M.; Zhuang, H. L.;
Zhukov, V.; Zichichi, A.; Zuccon, P.; AMS Collaboration
Bibcode: 2021PhRvL.127A1102A
Altcode:
We present the precision measurement of the daily proton fluxes in
cosmic rays from May 20, 2011 to October 29, 2019 (a total of 2824
days or 114 Bartels rotations) in the rigidity interval from 1 to
100 GV based on 5.5 ×109 protons collected with the Alpha
Magnetic Spectrometer aboard the International Space Station. The proton
fluxes exhibit variations on multiple timescales. From 2014 to 2018,
we observed recurrent flux variations with a period of 27 days. Shorter
periods of 9 days and 13.5 days are observed in 2016. The strength of
all three periodicities changes with time and rigidity. The rigidity
dependence of the 27-day periodicity is different from the rigidity
dependences of 9-day and 13.5-day periods. Unexpectedly, the strength of
9-day and 13.5-day periodicities increases with increasing rigidities
up to ∼10 GV and ∼20 GV , respectively. Then the strength of the
periodicities decreases with increasing rigidity up to 100 GV.
Title: Mind the Gap: New Precise 14C Data Indicate the
Nature of Extreme Solar Particle Events
Authors: Usoskin, Ilya G.; Kovaltsov, Gennady A.
Bibcode: 2021GeoRL..4894848U
Altcode:
Extreme solar particle events of 775 CE, 994 CE, and 660
BCE are nearly two orders of magnitude stronger than those
observed instrumentally. Because of the large observational gap
between directly measured and historical events, it was unclear
whether they can be produced by the Sun "normally" or from an
unknown phenomenon. Recent works by Miyake et al. (2021, doi: https://doi.org/10.1029/2021GL093419)
and Brehm et al. (2021, https://doi.org/10.1038/s41561-020-00674-0)
start filling the gap with weaker yet extreme events approaching the
detectability threshold. More such events are expected to be found in
the future but the present result, if confirmed, would imply that the
extreme solar events likely represent the high-energy/low-probability
tail of the continuous distribution of solar eruptive events rather
than a new unknown type of events. However, more statistic is needed
for a solid conclusion. This would lead to better understanding of
the processes producing such events that is important for their risk
assessments for the modern technology.
Title: Multiple Sources of Solar High-energy Protons
Authors: Kocharov, Leon; Omodei, Nicola; Mishev, Alexander;
Pesce-Rollins, Melissa; Longo, Francesco; Yu, Sijie; Gary, Dale E.;
Vainio, Rami; Usoskin, Ilya
Bibcode: 2021ApJ...915...12K
Altcode:
During the 24th solar cycle, the Fermi Large Area Telescope (LAT)
has observed a total of 27 solar flares possessing delayed γ-ray
emission, including the exceptionally well-observed flare and coronal
mass ejection (CME) on 2017 September 10. Based on the Fermi/LAT data,
we plot, for the first time, maps of possible sources of the delayed
>100 MeV γ-ray emission of the 2017 September 10 event. The
long-lasting γ-ray emission is localized under the CME core. The
γ-ray spectrum exhibits intermittent changes in time, implying that
more than one source of high-energy protons was formed during the
flare-CME eruption. We find a good statistical correlation between
the γ-ray fluences of the Fermi/LAT-observed delayed events and
the products of corresponding CME speed and the square root of the
soft X-ray flare magnitude. Data support the idea that both flares
and CMEs jointly contribute to the production of subrelativistic and
relativistic protons near the Sun.
Title: Properties of a New Group of Cosmic Nuclei: Results from the
Alpha Magnetic Spectrometer on Sodium, Aluminum, and Nitrogen
Authors: Aguilar, M.; Cavasonza, L. Ali; Alpat, B.; Ambrosi,
G.; Arruda, L.; Attig, N.; Barao, F.; Barrin, L.; Bartoloni, A.;
Başeǧmez-du Pree, S.; Battiston, R.; Behlmann, M.; Beranek, B.;
Berdugo, J.; Bertucci, B.; Bindi, V.; Bollweg, K.; Borgia, B.;
Boschini, M. J.; Bourquin, M.; Bueno, E. F.; Burger, J.; Burger,
W. J.; Burmeister, S.; Cai, X. D.; Capell, M.; Casaus, J.; Castellini,
G.; Cervelli, F.; Chang, Y. H.; Chen, G. M.; Chen, G. R.; Chen,
H. S.; Chen, Y.; Cheng, L.; Chou, H. Y.; Chouridou, S.; Choutko,
V.; Chung, C. H.; Clark, C.; Coignet, G.; Consolandi, C.; Contin,
A.; Corti, C.; Cui, Z.; Dadzie, K.; Delgado, C.; Della Torre, S.;
Demirköz, M. B.; Derome, L.; Di Falco, S.; Di Felice, V.; Díaz, C.;
Dimiccoli, F.; von Doetinchem, P.; Dong, F.; Donnini, F.; Duranti, M.;
Egorov, A.; Eline, A.; Feng, J.; Fiandrini, E.; Fisher, P.; Formato,
V.; Freeman, C.; Gámez, C.; García-López, R. J.; Gargiulo, C.;
Gast, H.; Gervasi, M.; Giovacchini, F.; Gómez-Coral, D. M.; Gong,
J.; Goy, C.; Grabski, V.; Grandi, D.; Graziani, M.; Haino, S.; Han,
K. C.; Hashmani, R. K.; He, Z. H.; Heber, B.; Hsieh, T. H.; Hu, J. Y.;
Incagli, M.; Jang, W. Y.; Jia, Yi; Jinchi, H.; Khiali, B.; Kim, G. N.;
Kirn, Th.; Konyushikhin, M.; Kounina, O.; Kounine, A.; Koutsenko, V.;
Krasnopevtsev, D.; Kuhlman, A.; Kulemzin, A.; La Vacca, G.; Laudi, E.;
Laurenti, G.; Lazzizzera, I.; Lebedev, A.; Lee, H. T.; Lee, S. C.;
Li, J. Q.; Li, M.; Li, Q.; Li, S.; Li, J. H.; Li, Z. H.; Liang, J.;
Light, C.; Lin, C. H.; Lippert, T.; Liu, J. H.; Liu, Z.; Lu, S. Q.;
Lu, Y. S.; Luebelsmeyer, K.; Luo, J. Z.; Luo, Xi; Machate, F.; Mañá,
C.; Marín, J.; Marquardt, J.; Martin, T.; Martínez, G.; Masi, N.;
Maurin, D.; Medvedeva, T.; Menchaca-Rocha, A.; Meng, Q.; Mikhailov,
V. V.; Molero, M.; Mott, P.; Mussolin, L.; Negrete, J.; Nikonov,
N.; Nozzoli, F.; Oliva, A.; Orcinha, M.; Palermo, M.; Palmonari,
F.; Paniccia, M.; Pashnin, A.; Pauluzzi, M.; Pensotti, S.; Phan,
H. D.; Plyaskin, V.; Pohl, M.; Poluianov, S.; Qin, X.; Qu, Z. Y.;
Quadrani, L.; Rancoita, P. G.; Rapin, D.; Conde, A. Reina; Robyn,
E.; Rosier-Lees, S.; Rozhkov, A.; Rozza, D.; Sagdeev, R.; Schael,
S.; von Dratzig, A. Schulz; Schwering, G.; Seo, E. S.; Shakfa, Z.;
Shan, B. S.; Siedenburg, T.; Solano, C.; Song, J. W.; Song, X. J.;
Sonnabend, R.; Strigari, L.; Su, T.; Sun, Q.; Sun, Z. T.; Tacconi, M.;
Tang, X. W.; Tang, Z. C.; Tian, J.; Ting, Samuel C. C.; Ting, S. M.;
Tomassetti, N.; Torsti, J.; Tüysüz, C.; Urban, T.; Usoskin, I.;
Vagelli, V.; Vainio, R.; Valencia-Otero, M.; Valente, E.; Valtonen,
E.; Vázquez Acosta, M.; Vecchi, M.; Velasco, M.; Vialle, J. P.;
Wang, C. X.; Wang, L.; Wang, L. Q.; Wang, N. H.; Wang, Q. L.; Wang,
S.; Wang, X.; Wang, Yu; Wang, Z. M.; Wei, J.; Weng, Z. L.; Wu, H.;
Xiong, R. Q.; Xu, W.; Yan, Q.; Yang, Y.; Yashin, I. I.; Yi, H.; Yu,
Y. M.; Yu, Z. Q.; Zannoni, M.; Zhang, C.; Zhang, F.; Zhang, F. Z.;
Zhang, J. H.; Zhang, Z.; Zhao, F.; Zheng, C.; Zheng, Z. M.; Zhuang,
H. L.; Zhukov, V.; Zichichi, A.; Zuccon, P.; AMS Collaboration
Bibcode: 2021PhRvL.127b1101A
Altcode:
We report the properties of sodium (Na) and aluminum (Al) cosmic rays
in the rigidity range 2.15 GV to 3.0 TV based on 0.46 million sodium
and 0.51 million aluminum nuclei collected by the Alpha Magnetic
Spectrometer experiment on the International Space Station. We found
that Na and Al, together with nitrogen (N), belong to a distinct
cosmic ray group. In this group, we observe that, similar to the N
flux, both the Na flux and Al flux are well described by the sums of a
primary cosmic ray component (proportional to the silicon flux) and a
secondary cosmic ray component (proportional to the fluorine flux). The
fraction of the primary component increases with rigidity for the N,
Na, and Al fluxes and becomes dominant at the highest rigidities. The
Na /Si and Al /Si abundance ratios at the source, 0.036 ±0.003 for
Na /Si and 0.103 ±0.004 for Al /Si , are determined independent of
cosmic ray propagation.
Title: Modelling the evolution of the Sun's open and total magnetic
flux
Authors: Krivova, N. A.; Solanki, S. K.; Hofer, B.; Wu, C. -J.;
Usoskin, I. G.; Cameron, R.
Bibcode: 2021A&A...650A..70K
Altcode: 2021arXiv210315603K
Solar activity in all its varied manifestations is driven by the
magnetic field. Two global quantities are particularly important for
many purposes, the Sun's total and open magnetic flux, which can be
computed from sunspot number records using models. Such sunspot-driven
models, however, do not take into account the presence of magnetic
flux during grand minima, such as the Maunder minimum. Here we
present a major update of a widely used simple model, which now takes
into account the observation that the distribution of all magnetic
features on the Sun follows a single power law. The exponent of the
power law changes over the solar cycle. This allows for the emergence
of small-scale magnetic flux even when no sunspots have been present
for multiple decades and leads to non-zero total and open magnetic
flux also in the deepest grand minima, such as the Maunder minimum,
thus overcoming a major shortcoming of the earlier models. The results
of the updated model compare well with the available observations and
reconstructions of the solar total and open magnetic flux. This opens
up the possibility of improved reconstructions of the sunspot number
from time series of the cosmogenic isotope production rate.
Title: GLE # 67 Event on 2 November 2003: An Analysis of the Spectral
and Anisotropy Characteristics Using Verified Yield Function and
Detrended Neutron Monitor Data
Authors: Mishev, Alexander L.; Koldobskiy, Sergey A.; Kocharov,
Leon G.; Usoskin, Ilya G.
Bibcode: 2021SoPh..296...79M
Altcode:
During Solar Cycle 23 16 ground-level enhancement events were registered
by the global neutron monitor network. In this work we focus on the
period with increased solar activity during late October - early
November 2003 producing a sequence of three events, specifically on
ground-level enhancement GLE 67 on 2 November 2003. On the basis of an
analysis of neutron monitor and space-borne data we derived the spectra
and pitch-angle distribution of high-energy solar particles with their
dynamical evolution throughout the event. According to our analysis,
the best fit of the spectral and angular properties of solar particles
was obtained by a modified power-law rigidity spectrum and a double
Gaussian, respectively. The derived angular distribution is consistent
with the observations where an early count rate increase at Oulu neutron
monitor with asymptotic viewing direction in the anti-Sun direction was
registered. The quality of the fit and model constraints were assessed
by a forward modeling. The event integrated particle fluence was derived
using two different methods. The derived results are briefly discussed.
Title: Seven Decades of Neutron Monitors (1951-2019): Overview and
Evaluation of Data Sources
Authors: Väisänen, Pauli; Usoskin, Ilya; Mursula, Kalevi
Bibcode: 2021JGRA..12628941V
Altcode:
The worldwide network of neutron monitors (NMs) is the primary
instrument to study cosmic ray variability on time scales of up to 70
yr. Since the 1950s, 147 NMs with publicly available data have been in
operation, and their records are archived in and distributed through
different repositories and data sources. A comprehensive analysis of all
available NM data sets (300 data sets from 147 NMs) is performed here to
check the quality and consistency of the data. The data sources include
World Data Center for Cosmic Rays, the Neutron Monitor Database, the
Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radiowave
Propagation (IZMIRAN) and individual station/institution databases. It
was found that The data from the same NM can be nonidentical and of
different quality in different sources. We give and tabulate here a
recommendation for the optimal data source of each NM. We also present
here a list of 29 "prime" stations with the longest and most reliable
data. Verified data sets for these prime stations are provided as
supplementary information.
Title: Solar cyclic activity over the last millennium reconstructed
from annual 14C data
Authors: Usoskin, I. G.; Solanki, S. K.; Krivova, N. A.; Hofer, B.;
Kovaltsov, G. A.; Wacker, L.; Brehm, N.; Kromer, B.
Bibcode: 2021A&A...649A.141U
Altcode: 2021arXiv210315112U
Aims: The 11-year solar cycle (Schwabe cycle) is the dominant
pattern of solar magnetic activity reflecting the oscillatory dynamo
mechanism in the Sun's convection zone. Solar cycles have been
directly observed since 1700, while indirect proxy data suggest their
existence over a much longer period of time, but generally without
resolving individual cycles and their continuity. Here we reconstruct
individual solar cycles for the last millennium using recently
obtained 14C data and state-of-the-art models.
Methods: Starting with the 14C production rate determined
from the so far most precise measurements of radiocarbon content in
tree rings, solar activity was reconstructed in the following three
physics-based steps: (1) correction of the 14C production
rate for the changing geomagnetic field; (2) computation of the
open solar magnetic flux; and (3) conversion into sunspot numbers
outside of grand minima. All known uncertainties, including both
measurement and model uncertainties, were straightforwardly accounted
for by a Monte-Carlo method.
Results: Cyclic solar activity is
reconstructed for the period 971-1900 (85 individual cycles) along with
its uncertainties. This more than doubles the number of solar cycles
known from direct solar observations. We found that the lengths and
strengths of well-defined cycles outside grand minima are consistent
with those obtained from the direct sunspot observations after 1750. The
validity of the Waldmeier rule (cycles with fast-rising phase tend to
be stronger) is confirmed at a highly significant level. Solar activity
is found to be in a deep grand minimum when the activity is mostly
below the sunspot formation threshold for about 250 years. Therefore,
although considerable cyclic variability in 14C is seen even
during grand minima, individual solar cycles can hardly be reliably
resolved therein. Three potential solar particle events, ca. 994,
1052, and 1279 AD, are shown to occur around the maximum phases of
solar cycles.
Conclusions: A new approximately 1000-year-long
solar activity reconstruction, in the form of annual (pseudo) sunspot
numbers with the full assessment of all known uncertainties, is
presented based on new high-precision Δ14C measurements and
state-of-the-art models, more than doubling the number of individually
resolved solar cycles. This forms a solid basis for new, more detailed
studies of solar variability. Tabular data of the reconstructed
activity are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/649/A141
Title: High Altitude Polar NM With the New DAQ System as a Tool to
Study Details of the Cosmic Ray Induced Nucleonic Cascade
Authors: Similä, Markus; Usoskin, Ilya; Poluianov, Stepan; Mishev,
Alexander; Kovaltsov, Gennady A.; Strauss, Du Toit
Bibcode: 2021JGRA..12628959S
Altcode: 2021arXiv210404727S
A neutron monitor (NM) is, since the 1950s, a standard ground based
detector whose count rate reflects cosmic ray variability. The worldwide
network of NMs forms a rough spectrometer for cosmic rays. Recently, a
brand new data acquisition (DAQ) system has been installed on the DOMC
and DOMB NMs, located at the Concordia research station on the Central
Antarctic plateau. The new DAQ system digitizes, at a 2 MHz sampling
rate, and records all individual pulses corresponding to secondary
particles in the detector. An analysis of the pulse characteristics
(viz. shape, magnitude, duration, waiting time) has been performed,
and several clearly distinguishable branches were identified: (A)
corresponding to signal from individual secondary neutrons; (B)
representing the detector's noise; (C) double pulses corresponding
to the shortly separated nucleons of the same atmospheric cascades;
(D) very high multiple pulses which are likely caused by atmospheric
muons; and (E) double pulses potentially caused by contamination of the
neighboring detector. An analysis of the waiting time distributions has
revealed two clearly distinguishable peaks: peak (I) at about 1 ms being
related to the intracascade diffusion and thermalization of secondary
atmospheric neutrons; and peak (II) at 30-1,000 ms corresponding to
individual atmospheric cascades. This opens a new possibility to study
spectra of cosmic ray particles in a single location as well as details
of the cosmic ray induced atmospheric cascades, using the same data set.
Title: Atmospheric production and transport of 7Be activity by
cosmic rays: Modelling with the chemistry-climate model SOCOLv3.0
and comparison with direct measurements
Authors: Golubenko, Kseniia; Rozanov, Eugene; Kovaltsov, Genady;
Leppänen, Ari-Pekka; Usoskin, Ilya
Bibcode: 2021EGUGA..23.2287G
Altcode:
We present the first results of modelling of the short-living
cosmogenic isotope 7Be production, deposition, and transport using the
chemistry-climate model SOCOLv3.0 aimed to study solar-terrestrial
interactions and climate changes. We implemented an interactive
deposition scheme, based on gas tracers with and without nudging to
the known meteorological fields. Production of 7Be was modelled using
the 3D time-dependent Cosmic Ray induced Atmospheric Cascade (CRAC)
model. The simulations were compared with the real concentrations
(activity) and depositions measurements of 7Be in the air and water at
Finnish stations. We have successfully reproduced and estimated the
variability of the cosmogenic isotope 7Be produced by the galactic
cosmic rays (GCR) on time scales longer than about a month, for the
period of 2002-2008. The agreement between the modelled and measured
data is very good (within 12%) providing a solid validation for the
ability of the SOCOL CCM to reliably model production, transport,
and deposition of cosmogenic isotopes, which is needed for precise
studies of cosmic-ray variability in the past.
Title: New reconstruction of event-integrated spectra (spectral
fluences) for major solar energetic particle events
Authors: Koldobskiy, S.; Raukunen, O.; Vainio, R.; Kovaltsov, G. A.;
Usoskin, I.
Bibcode: 2021A&A...647A.132K
Altcode: 2021arXiv210110234K
Aims: Fluences of solar energetic particles (SEPs) are not
easy to evaluate, especially for high-energy events (i.e. ground-level
enhancements, GLEs). Earlier estimates of event-integrated SEP fluences
for GLEs were based on partly outdated assumptions and data, and they
required revisions. Here, we present the results of a full revision
of the spectral fluences for most major SEP events (GLEs) for the
period from 1956 to 2017 using updated low-energy flux estimates along
with greatly revisited high-energy flux data and applying the newly
invented reconstruction method including an improved neutron-monitor
yield function.
Methods: Low- and high-energy parts of the
SEP fluence were estimated using a revised space-borne/ionospheric
data and ground-based neutron monitors, respectively. The measured
data were fitted by the modified Band function spectral shape. The
best-fit parameters and their uncertainties were assessed using a
direct Monte Carlo method.
Results: A full reconstruction of
the event-integrated spectral fluences was performed in the energy
range above 30 MeV, parametrised and tabulated for easy use along
with estimates of the 68% confidence intervals.
Conclusions:
This forms a solid basis for more precise studies of the physics of
solar eruptive events and the transport of energetic particles in the
interplanetary medium, as well as the related applications. The
reconstructed fluences in tabulated form and the corresponding best-fit
parameters are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/647/A132
Title: VizieR Online Data Catalog: 1000-year sunspot series (Usoskin+,
2021)
Authors: Usoskin, I. G.; Solanki, S. K.; Krivova, N.; Hofer, B.;
Kovaltsov, G. A.; Wacker, L.; Brehm, N.; Kromer, B.
Bibcode: 2021yCat..36490141U
Altcode:
A new quantitative reconstruction of annually resolved solar activity,
in the form of SNs (at least outside grand minima) with a full
uncertainty assessment, is presented for the period 971-1900. For the
first time, individual solar cycles are presented for the whole of the
last millennium, more than doubling the existing statistics of solar
cycles. Three tabular files are presented. File 'osf.dat'
contains annual reconstructions of the opens solar flux (OSF) [Fo]
along with its 1-sigma uncertainties [sF] and the smoothed (22-yr SSA --
see text) values [<Fo>]. This table corresponds to Figure 8 in
the text. File 'osn.dat' contains annual reconstructions of the
sunspot number (SN) [SN] along with its 1-sigma uncertainties [sSN]
and the smoothed (22-yr SSA -- see text) values [<SN>]. This
table corresponds to Figure 11 in the text. File 'table1.dat'
presents a textual tabular version of Table 1 in the text and contains
the internal cycle number [n], years of minimum [Ymin] and maximum
[Ymax] of each cycle, cycle-averaged sunspot number [<SN>], its
1-sigma uncertainty [sS], cycle length (min-to-min) [T], and quality
flag [q]. (3 data files).
Title: The Alpha Magnetic Spectrometer (AMS) on the international
space station: Part II - Results from the first seven years
Authors: Aguilar, M.; Ali Cavasonza, L.; Ambrosi, G.; Arruda, L.;
Attig, N.; Barao, F.; Barrin, L.; Bartoloni, A.; Başeğmez-du Pree,
S.; Bates, J.; Battiston, R.; Behlmann, M.; Beischer, B.; Berdugo,
J.; Bertucci, B.; Bindi, V.; de Boer, W.; Bollweg, K.; Borgia, B.;
Boschini, M. J.; Bourquin, M.; Bueno, E. F.; Burger, J.; Burger,
W. J.; Burmeister, S.; Cai, X. D.; Capell, M.; Casaus, J.; Castellini,
G.; Cervelli, F.; Chang, Y. H.; Chen, G. M.; Chen, H. S.; Chen, Y.;
Cheng, L.; Chou, H. Y.; Chouridou, S.; Choutko, V.; Chung, C. H.;
Clark, C.; Coignet, G.; Consolandi, C.; Contin, A.; Corti, C.; Cui,
Z.; Dadzie, K.; Dai, Y. M.; Delgado, C.; Della Torre, S.; Demirköz,
M. B.; Derome, L.; Di Falco, S.; Di Felice, V.; Díaz, C.; Dimiccoli,
F.; von Doetinchem, P.; Dong, F.; Donnini, F.; Duranti, M.; Egorov, A.;
Eline, A.; Feng, J.; Fiandrini, E.; Fisher, P.; Formato, V.; Freeman,
C.; Galaktionov, Y.; Gámez, C.; García-López, R. J.; Gargiulo, C.;
Gast, H.; Gebauer, I.; Gervasi, M.; Giovacchini, F.; Gómez-Coral,
D. M.; Gong, J.; Goy, C.; Grabski, V.; Grandi, D.; Graziani, M.;
Guo, K. H.; Haino, S.; Han, K. C.; Hashmani, R. K.; He, Z. H.; Heber,
B.; Hsieh, T. H.; Hu, J. Y.; Huang, Z. C.; Hungerford, W.; Incagli,
M.; Jang, W. Y.; Jia, Yi; Jinchi, H.; Kanishev, K.; Khiali, B.;
Kim, G. N.; Kirn, Th.; Konyushikhin, M.; Kounina, O.; Kounine, A.;
Koutsenko, V.; Kuhlman, A.; Kulemzin, A.; La Vacca, G.; Laudi, E.;
Laurenti, G.; Lazzizzera, I.; Lebedev, A.; Lee, H. T.; Lee, S. C.;
Leluc, C.; Li, J. Q.; Li, M.; Li, Q.; Li, S.; Li, T. X.; Li, Z. H.;
Light, C.; Lin, C. H.; Lippert, T.; Liu, Z.; Lu, S. Q.; Lu, Y. S.;
Luebelsmeyer, K.; Luo, J. Z.; Lyu, S. S.; Machate, F.; Mañá, C.;
Marín, J.; Marquardt, J.; Martin, T.; Martínez, G.; Masi, N.; Maurin,
D.; Menchaca-Rocha, A.; Meng, Q.; Mo, D. C.; Molero, M.; Mott, P.;
Mussolin, L.; Ni, J. Q.; Nikonov, N.; Nozzoli, F.; Oliva, A.; Orcinha,
M.; Palermo, M.; Palmonari, F.; Paniccia, M.; Pashnin, A.; Pauluzzi,
M.; Pensotti, S.; Phan, H. D.; Plyaskin, V.; Pohl, M.; Porter, S.; Qi,
X. M.; Qin, X.; Qu, Z. Y.; Quadrani, L.; Rancoita, P. G.; Rapin, D.;
Reina Conde, A.; Rosier-Lees, S.; Rozhkov, A.; Rozza, D.; Sagdeev,
R.; Schael, S.; Schmidt, S. M.; Schulz von Dratzig, A.; Schwering,
G.; Seo, E. S.; Shan, B. S.; Shi, J. Y.; Siedenburg, T.; Solano,
C.; Song, J. W.; Sonnabend, R.; Sun, Q.; Sun, Z. T.; Tacconi, M.;
Tang, X. W.; Tang, Z. C.; Tian, J.; Ting, Samuel C. C.; Ting, S. M.;
Tomassetti, N.; Torsti, J.; Tüysüz, C.; Urban, T.; Usoskin, I.;
Vagelli, V.; Vainio, R.; Valente, E.; Valtonen, E.; Vázquez Acosta,
M.; Vecchi, M.; Velasco, M.; Vialle, J. P.; Wang, L. Q.; Wang, N. H.;
Wang, Q. L.; Wang, S.; Wang, X.; Wang, Z. X.; Wei, J.; Weng, Z. L.;
Wu, H.; Xiong, R. Q.; Xu, W.; Yan, Q.; Yang, Y.; Yi, H.; Yu, Y. J.;
Yu, Z. Q.; Zannoni, M.; Zhang, C.; Zhang, F.; Zhang, F. Z.; Zhang,
J. H.; Zhang, Z.; Zhao, F.; Zheng, Z. M.; Zhuang, H. L.; Zhukov, V.;
Zichichi, A.; Zimmermann, N.; Zuccon, P.; AMS Collaboration
Bibcode: 2021PhR...894....1A
Altcode:
The Alpha Magnetic Spectrometer (AMS) is a precision particle physics
detector on the International Space Station (ISS) conducting a unique,
long-duration mission of fundamental physics research in space. The
physics objectives include the precise studies of the origin of dark
matter, antimatter, and cosmic rays as well as the exploration of new
phenomena. Following a 16-year period of construction and testing, and
a precursor flight on the Space Shuttle, AMS was installed on the ISS
on May 19, 2011. In this report we present results based on 120 billion
charged cosmic ray events up to multi-TeV energies. This includes the
fluxes of positrons, electrons, antiprotons, protons, and nuclei. These
results provide unexpected information, which cannot be explained by
the current theoretical models. The accuracy and characteristics of
the data, simultaneously from many different types of cosmic rays,
provide unique input to the understanding of origins, acceleration,
and propagation of cosmic rays.
Title: Application of the Verified Neutron Monitor Yield Function
for an Extended Analysis of the GLE # 71 on 17 May 2012
Authors: Mishev, A. L.; Koldobskiy, S. A.; Usoskin, I. G.; Kocharov,
L. G.; Kovaltsov, G. A.
Bibcode: 2021SpWea..1902626M
Altcode:
Intense solar activity was observed in May 2012. A notable ground
level enhancement (GLE) was registered on 17 May 2012 by several
space borne instruments as well as on ground by neutron monitors
(NMs). This event is known as GLE # 71. Here, we derived the spectral
and angular characteristics, and apparent source position of the solar
protons during the GLE # 71, employing verified newly computed NM
yield function and sophisticated unfolding procedure. We considerably
improved the previously derived information about the spectra and
angular distribution, namely, the precision, time span, and time
resolution of the derived characteristics, specifically during the
event onset and late phase. A comparison with direct measurements,
with the Payload for Antimatter Matter Exploration and Light nuclei
Astrophysics (PAMELA) experiment, of the particle fluence was performed,
and good agreement between NM and direct space borne data analysis was
achieved. Subsequently, we computed the effective dose rates in the
polar region at several altitudes during the event using the derived
rigidity spectra of the solar protons as a reliable input for the
corresponding radiation model. The contribution of the galactic cosmic
rays and solar protons to the exposure is explicitly considered. We
computed the integrated exposure during the event and discussed the
exposure of crew members/passengers to radiation at several altitudes.
Title: Properties of Heavy Secondary Fluorine Cosmic Rays: Results
from the Alpha Magnetic Spectrometer
Authors: Aguilar, M.; Cavasonza, L. Ali; Allen, M. S.; Alpat, B.;
Ambrosi, G.; Arruda, L.; Attig, N.; Barao, F.; Barrin, L.; Bartoloni,
A.; Başeǧmez-du Pree, S.; Battiston, R.; Behlmann, M.; Beranek,
B.; Berdugo, J.; Bertucci, B.; Bindi, V.; Bollweg, K.; Borgia, B.;
Boschini, M. J.; Bourquin, M.; Bueno, E. F.; Burger, J.; Burger, W. J.;
Burmeister, S.; Cai, X. D.; Capell, M.; Casaus, J.; Castellini, G.;
Cervelli, F.; Chang, Y. H.; Chen, G. M.; Chen, G. R.; Chen, H. S.;
Chen, Y.; Cheng, L.; Chou, H. Y.; Chouridou, S.; Choutko, V.; Chung,
C. H.; Clark, C.; Coignet, G.; Consolandi, C.; Contin, A.; Corti, C.;
Cui, Z.; Dadzie, K.; Delgado, C.; Della Torre, S.; Demirköz, M. B.;
Derome, L.; Di Falco, S.; Di Felice, V.; Díaz, C.; Dimiccoli, F.;
von Doetinchem, P.; Dong, F.; Donnini, F.; Duranti, M.; Egorov, A.;
Eline, A.; Feng, J.; Fiandrini, E.; Fisher, P.; Formato, V.; Freeman,
C.; Galaktionov, Y.; Gámez, C.; García-López, R. J.; Gargiulo,
C.; Gast, H.; Gervasi, M.; Giovacchini, F.; Gómez-Coral, D. M.;
Gong, J.; Goy, C.; Grabski, V.; Grandi, D.; Graziani, M.; Haino, S.;
Han, K. C.; Hashmani, R. K.; He, Z. H.; Heber, B.; Hsieh, T. H.; Hu,
J. Y.; Incagli, M.; Jang, W. Y.; Jia, Yi; Jinchi, H.; Kanishev, K.;
Khiali, B.; Kim, G. N.; Kirn, Th.; Konyushikhin, M.; Kounina, O.;
Kounine, A.; Koutsenko, V.; Kuhlman, A.; Kulemzin, A.; La Vacca, G.;
Laudi, E.; Laurenti, G.; Lazzizzera, I.; Lebedev, A.; Lee, H. T.;
Lee, S. C.; Li, J. Q.; Li, M.; Li, Q.; Li, S.; Li, J. H.; Li, Z. H.;
Liang, J.; Light, C.; Lin, C. H.; Lippert, T.; Liu, J. H.; Liu, Z.;
Lu, S. Q.; Lu, Y. S.; Luebelsmeyer, K.; Luo, J. Z.; Luo, Xi; Lyu,
S. S.; Machate, F.; Mañá, C.; Marín, J.; Marquardt, J.; Martin,
T.; Martínez, G.; Masi, N.; Maurin, D.; Menchaca-Rocha, A.; Meng,
Q.; Mikhailov, V. V.; Mo, D. C.; Molero, M.; Mott, P.; Mussolin,
L.; Negrete, J.; Nikonov, N.; Nozzoli, F.; Oliva, A.; Orcinha, M.;
Palermo, M.; Palmonari, F.; Paniccia, M.; Pashnin, A.; Pauluzzi, M.;
Pensotti, S.; Phan, H. D.; Piandani, R.; Plyaskin, V.; Poluianov,
S.; Qin, X.; Qu, Z. Y.; Quadrani, L.; Rancoita, P. G.; Rapin, D.;
Conde, A. Reina; Robyn, E.; Rosier-Lees, S.; Rozhkov, A.; Rozza, D.;
Sagdeev, R.; Schael, S.; Schulz von Dratzig, A.; Schwering, G.; Seo,
E. S.; Shakfa, Z.; Shan, B. S.; Siedenburg, T.; Solano, C.; Song,
J. W.; Song, X. J.; Sonnabend, R.; Strigari, L.; Su, T.; Sun, Q.;
Sun, Z. T.; Tacconi, M.; Tang, X. W.; Tang, Z. C.; Tian, J.; Ting,
Samuel C. C.; Ting, S. M.; Tomassetti, N.; Torsti, J.; Tüysüz, C.;
Urban, T.; Usoskin, I.; Vagelli, V.; Vainio, R.; Valencia-Otero, M.;
Valente, E.; Valtonen, E.; Vázquez Acosta, M.; Vecchi, M.; Velasco,
M.; Vialle, J. P.; Wang, C. X.; Wang, L.; Wang, L. Q.; Wang, N. H.;
Wang, Q. L.; Wang, S.; Wang, X.; Wang, Yu; Wang, Z. M.; Wei, J.; Weng,
Z. L.; Wu, H.; Xiong, R. Q.; Xu, W.; Yan, Q.; Yang, Y.; Yashin, I. I.;
Yi, H.; Yu, Y. M.; Yu, Z. Q.; Zannoni, M.; Zhang, C.; Zhang, F.; Zhang,
F. Z.; Zhang, J. H.; Zhang, Z.; Zhao, F.; Zheng, C.; Zheng, Z. M.;
Zhuang, H. L.; Zhukov, V.; Zichichi, A.; Zuccon, P.; AMS Collaboration
Bibcode: 2021PhRvL.126h1102A
Altcode:
Precise knowledge of the charge and rigidity dependence of the
secondary cosmic ray fluxes and the secondary-to-primary flux ratios is
essential in the understanding of cosmic ray propagation. We report the
properties of heavy secondary cosmic ray fluorine F in the rigidity
R range 2.15 GV to 2.9 TV based on 0.29 million events collected
by the Alpha Magnetic Spectrometer experiment on the International
Space Station. The fluorine spectrum deviates from a single power
law above 200 GV. The heavier secondary-to-primary F/Si flux ratio
rigidity dependence is distinctly different from the lighter B/O (or
B/C) rigidity dependence. In particular, above 10 GV, the F//Si B /O
ratio can be described by a power law Rδ with δ =0.052
±0.007 . This shows that the propagation properties of heavy cosmic
rays, from F to Si, are different from those of light cosmic rays,
from He to O, and that the secondary cosmic rays have two classes.
Title: Robustness of Solar-Cycle Empirical Rules Across Different
Series Including an Updated Active-Day Fraction (ADF) Sunspot
Group Series
Authors: Usoskin, Ilya; Kovaltsov, Gennady; Kiviaho, Wilma
Bibcode: 2021SoPh..296...13U
Altcode: 2020arXiv201208415U
Empirical rules of solar-cycle evolution form important observational
constraints for the solar-dynamo theory. This includes the Waldmeier
rule relating the magnitude of a solar cycle to the length of its
ascending phase, and the Gnevyshev-Ohl rule clustering cycles to
pairs of an even-numbered cycle followed by a stronger odd-numbered
cycle. These rules were established as based on the "classical" Wolf
sunspot number series, which has been essentially revisited recently,
with several revised sets released by the research community. Here we
test the robustness of these empirical rules for different sunspot
(group) series for the period 1749 - 1996, using four classical
and revised international sunspot-number and group sunspot-number
series. We also provide an update of the sunspot-group series based
on the active-day fraction (ADF) method, using the new database of
solar observations. We show that the Waldmeier rule is robust and
independent of the exact sunspot (group) series: its classical and n +1
(relating the length of n th cycle to the magnitude of (n +1 )th cycle)
formulations are significant or highly significant for all series,
while its simplified formulation (relating the magnitude of a cycle to
its full length) is insignificant for all series. The Gnevyshev-Ohl
rule was found robust for all analyzed series for Solar Cycles 8 -
21, but unstable across the Dalton minimum and before it.
Title: Properties of Iron Primary Cosmic Rays: Results from the
Alpha Magnetic Spectrometer
Authors: Aguilar, M.; Cavasonza, L. Ali; Allen, M. S.; Alpat, B.;
Ambrosi, G.; Arruda, L.; Attig, N.; Barao, F.; Barrin, L.; Bartoloni,
A.; Başeǧmez-du Pree, S.; Battiston, R.; Behlmann, M.; Beischer,
B.; Berdugo, J.; Bertucci, B.; Bindi, V.; de Boer, W.; Bollweg, K.;
Borgia, B.; Boschini, M. J.; Bourquin, M.; Bueno, E. F.; Burger, J.;
Burger, W. J.; Burmeister, S.; Cai, X. D.; Capell, M.; Casaus, J.;
Castellini, G.; Cervelli, F.; Chang, Y. H.; Chen, G. M.; Chen, G. R.;
Chen, H. S.; Chen, Y.; Cheng, L.; Chou, H. Y.; Chouridou, S.; Choutko,
V.; Chung, C. H.; Clark, C.; Coignet, G.; Consolandi, C.; Contin,
A.; Corti, C.; Cui, Z.; Dadzie, K.; Delgado, C.; Della Torre, S.;
Demirköz, M. B.; Derome, L.; Di Falco, S.; Di Felice, V.; Díaz, C.;
Dimiccoli, F.; von Doetinchem, P.; Dong, F.; Donnini, F.; Duranti, M.;
Egorov, A.; Eline, A.; Feng, J.; Fiandrini, E.; Fisher, P.; Formato,
V.; Freeman, C.; Galaktionov, Y.; Gámez, C.; García-López, R. J.;
Gargiulo, C.; Gast, H.; Gervasi, M.; Giovacchini, F.; Gómez-Coral,
D. M.; Gong, J.; Goy, C.; Grabski, V.; Grandi, D.; Graziani, M.; Haino,
S.; Han, K. C.; Hashmani, R. K.; He, Z. H.; Heber, B.; Hsieh, T. H.;
Hu, J. Y.; Incagli, M.; Jang, W. Y.; Jia, Yi; Jinchi, H.; Kanishev,
K.; Khiali, B.; Kim, G. N.; Kirn, Th.; Konyushikhin, M.; Kounina,
O.; Kounine, A.; Koutsenko, V.; Kuhlman, A.; Kulemzin, A.; La Vacca,
G.; Laudi, E.; Laurenti, G.; Lazzizzera, I.; Lebedev, A.; Lee, H. T.;
Lee, S. C.; Li, J. Q.; Li, M.; Li, Q.; Li, S.; Li, J. H.; Li, Z. H.;
Liang, J.; Light, C.; Lin, C. H.; Lippert, T.; Liu, J. H.; Liu, Z.;
Lu, S. Q.; Lu, Y. S.; Luebelsmeyer, K.; Luo, J. Z.; Luo, Xi; Lyu,
S. S.; Machate, F.; Mañá, C.; Marín, J.; Marquardt, J.; Martin,
T.; Martínez, G.; Masi, N.; Maurin, D.; Menchaca-Rocha, A.; Meng,
Q.; Mikhailov, V. V.; Mo, D. C.; Molero, M.; Mott, P.; Mussolin,
L.; Negrete, J.; Nikonov, N.; Nozzoli, F.; Oliva, A.; Orcinha, M.;
Palermo, M.; Palmonari, F.; Paniccia, M.; Pashnin, A.; Pauluzzi, M.;
Pensotti, S.; Phan, H. D.; Piandani, R.; Plyaskin, V.; Poluianov,
S.; Qin, X.; Qu, Z. Y.; Quadrani, L.; Rancoita, P. G.; Rapin, D.;
Conde, A. Reina; Robyn, E.; Rosier-Lees, S.; Rozhkov, A.; Rozza, D.;
Sagdeev, R.; Schael, S.; von Dratzig, A. Schulz; Schwering, G.; Seo,
E. S.; Shakfa, Z.; Shan, B. S.; Siedenburg, T.; Solano, C.; Song,
J. W.; Song, X. J.; Sonnabend, R.; Strigari, L.; Su, T.; Sun, Q.;
Sun, Z. T.; Tacconi, M.; Tang, X. W.; Tang, Z. C.; Tian, J.; Ting,
Samuel C. C.; Ting, S. M.; Tomassetti, N.; Torsti, J.; Tüysüz, C.;
Urban, T.; Usoskin, I.; Vagelli, V.; Vainio, R.; Valencia-Otero, M.;
Valente, E.; Valtonen, E.; Vázquez Acosta, M.; Vecchi, M.; Velasco,
M.; Vialle, J. P.; Wang, C. X.; Wang, L.; Wang, L. Q.; Wang, N. H.;
Wang, Q. L.; Wang, S.; Wang, X.; Wang, Yu; Wang, Z. M.; Wei, J.;
Weng, Z. L.; Wu, H.; Xiong, R. Q.; Xu, W.; Yan, Q.; Yang, Y.; Yashin,
I. I.; Yi, H.; Yu, Y. M.; Yu, Z. Q.; Zannoni, M.; Zhang, C.; Zhang,
F.; Zhang, F. Z.; Zhang, J. H.; Zhang, Z.; Zhao, F.; Zheng, C.;
Zheng, Z. M.; Zhuang, H. L.; Zhukov, V.; Zichichi, A.; Zimmermann,
N.; Zuccon, P.; AMS Collaboration
Bibcode: 2021PhRvL.126d1104A
Altcode:
We report the observation of new properties of primary iron (Fe) cosmic
rays in the rigidity range 2.65 GV to 3.0 TV with 0.62 ×106
iron nuclei collected by the Alpha Magnetic Spectrometer experiment on
the International Space Station. Above 80.5 GV the rigidity dependence
of the cosmic ray Fe flux is identical to the rigidity dependence of
the primary cosmic ray He, C, and O fluxes, with the Fe /O flux ratio
being constant at 0.155 ±0.006 . This shows that unexpectedly Fe and
He, C, and O belong to the same class of primary cosmic rays which is
different from the primary cosmic rays Ne, Mg, and Si class.
Title: VizieR Online Data Catalog: GLE integral intensities
(Koldobskiy+, 2021)
Authors: Koldobskiy, S.; Raukunen, O.; Vainio, R.; Kovaltsov, G. A.;
Usoskin, I.
Bibcode: 2021yCat..36470132K
Altcode:
File params.dat contains parameters of the modified Band-function
fit of the integral flux (fluence) for SEP registered by satellite/
ionospheric experiments and neutron monitor network (58 most powerful
GLE events). Each string corresponds to the separate GLE event File fluences.dat contains ready-to-use fluences (in units of
cm-2) of solar energetic particles for 58 considered GLE
events (GLE # and date are given for event identification). Fluences
are obtained using best MBF fit and are given in log-space scale from
0.239GV to 20GV. Fluences corresponding to energies >100, >430
and >1000MeV are also given. (2 data files).
Title: International Space Weather Action Team (ISWAT) S1: Long-term
Solar Variability
Authors: Nandi, Dibyendu; Usoskin, Ilya; Pevtsov, Alexei
Bibcode: 2021cosp...43E2412N
Altcode:
The COSPAR International Space Weather Action Team (ISWAT) is a global
hub for space weather community efforts toward the realization
of the International Living With a Star-COSPAR Space Weather
Roadmap goals. The community provides an inclusive environment for
collaborative research efforts, information sharing and capacity
building in the space weather sciences with a specific focus on
enabling prediction and applications. Action teams within ISWAT
address a specific focussed topic around which the team expertise
is built. In this poster presentation we highlight the ISWAT Action
Team S1 (Long term solar variability). The team is motivated towards
understanding solar drivers of long term variability in the heliospheric
space environment, its impact on geospace and other planets. This
ISWAT Team is moderated by Dibyendu Nandi, Ilya Usoskin and Alexei
Pevtsov. Interested scientists can join the team through the ISWAT
website at: https://iswat-cospar.org/.
Title: Validation of the updated neutron monitor yield function via
data from AMS-02
Authors: Gil, Agnieszka; Usoskin, Ilya; Koldobskiy, Sergey; Kovaltsov,
Gennady A.; Mishev, Alexander
Bibcode: 2021cosp...43E.861G
Altcode:
We present an updated yield function (YF), along with the corresponding
parametrization, for the standard neutron monitor (NM), 6NM64, for both
primary protons and ????-particles (the latter effectively includes
heavier species). The updated YF was computed using the Mishev et
al. (2013) approach, based on a full Monte Carlo simulations of the
cosmic-ray induced atmospheric cascade, for different altitudes,
covering the entire range of locations, from sea level to 500 g/cm$
^{2}$ (∼5.7 km). The validation of the updated YF was done by
applying the cosmic-ray spectra directly measured in situ by the
AMS-02 experiment for 79 Bartels rotations, from May 2011 through May
2017. We confronted the modeled results with the measured count rates
of all NM64 neutron monitors operating during the studied period. We
also obtained the scaling factors $\kappa$, being the ratio of the
computed to the measured NM count rates, assessing the stability of
all the selected NMs. A list of stable NMs is provided.
Title: COSPAR International Space Weather Action Teams: Addressing
Challenges Across the Field of Space Weather.
Authors: Kuznetsova, M. M.; Belehaki, A.; Bisi, M. M.; Bruinsma, S.;
Fung, S. F.; Glover, A.; Grande, M.; Guo, J.; Jun, I.; Linker, J.;
Mann, I. R.; Masson, A.; Mendoza, A. M. M.; Murray, S. A.; Nandy, D.;
Opgenoorth, H. J.; Pevtsov, A. A.; Plainaki, C.; Reiss, M.; Sutton,
E. K.; Temmer, M.; Usoskin, I. G.; Yao, Z.; Yardley, S.; Zheng, Y.
Bibcode: 2020AGUFMSH0030022K
Altcode:
Advanced predictions of space weather impacts require improved
understanding and modeling capabilities of coupled chains of space
environment processes. It is necessary to assemble parts of the
source-to-impact puzzle by identifying, addressing and solving
problems focused on specific physical domains, and then to connect
all validated solutions from space weather origins on the sun to
impacts on coupled geospace system, humans and technologies. To
address the need for multi-disciplinary international space weather
research community connecting experts in space weather phenomena
across all domains and experts in space environment impact,
the COSPAR Panel on Space Weather facilitated establishment of
a network of International Space Weather Action Teams (ISWAT, https://www.iswat-cospar.org,
@IswatCosparOrg). ISWAT serves as a global hub for community coordinated
topical collaborations focused on different aspects of space weather
including advancing understanding, assessment and improvement of
modeling capabilities, transitioning advances in research to operations,
optimized utilization of available observations, and generating inputs
to future instrumentation deployment. Action teams are building
blocks of ISWAT initiative. ISWAT action teams are organized into
domain-based ISWAT clusters. Action teams are working in coordinated
effort across physical domain and across borders. The primary ISWAT
goal is to advance space weather predictive capabilities based on best
science available. The ISWAT currently includes more than 250 active
participants and more than 50 action teams. The presentation will
overview the outcome from the COSPAR ISWAT Inaugural Working Meeting
in February 2020, highlight recent progress in advancing physics-based
predictive capabilities and discuss plans for transforming COSPAR space
weather Roadmap into a living document maintained by the community.
Title: A New Full 3-D Model of Cosmogenic Tritium 3H
Production in the Atmosphere (CRAC:3H)
Authors: Poluianov, S. V.; Kovaltsov, G. A.; Usoskin, I. G.
Bibcode: 2020JGRD..12533147P
Altcode: 2020arXiv200907700P
A new model of cosmogenic tritium (3H) production in the
atmosphere is presented. The model belongs to the CRAC (Cosmic Ray
Atmospheric Cascade) family and is named as CRAC:3H. It is based on
a full Monte Carlo simulation of the cosmic ray induced atmospheric
cascade using the Geant4 toolkit. The CRAC:3H model is able, for the
first time, to compute tritium production at any location and time, for
any given energy spectrum of the primary incident cosmic ray particles,
explicitly treating, also for the first time, particles heavier than
protons. This model provides a useful tool for the use of 3H
as a tracer of atmospheric and hydrological circulation. A numerical
recipe for practical use of the model is appended.
Title: Revised GLE database: Fluences of solar energetic particles
as measured by the neutron-monitor network since 1956
Authors: Usoskin, I.; Koldobskiy, S.; Kovaltsov, G. A.; Gil, A.;
Usoskina, I.; Willamo, T.; Ibragimov, A.
Bibcode: 2020A&A...640A..17U
Altcode:
Aims: Continuous measurements of ground-based neutron
monitors (NMs) form the main data source for studying high-energy
high-intensity solar energetic particle (SEP) events that are called
ground-level enhancements (GLEs). All available data are collected
in the International GLE Database (IGLED), which provides formal NM
count-rate increases above the constant pre-increase level which is due
to galactic cosmic rays (GCR). This data set is used to reconstruct the
energy spectra of GLE events. However, the assumption of a constant
GCR background level throughout GLE events is often invalid. Here we
thoroughly revise the IGLED and provide a data set of detrended NM
count-rate increases that accounts for the variable GCR background.
Methods: The formal GLE count-rate increases were corrected for
the variable GCR background, which may vary significantly during GLE
events. The corresponding integral omnidirectional fluences of SEPs
were reconstructed for all GLEs with sufficient strength from the
detrended data using the effective rigidity method.
Results:
The database of the detrended NM count rate is revised for GLE events
since 1956. Integral omnidirectional fluences were estimated for 58
GLE events and parametrised for 52 sufficiently strong events using
the modified Ellison-Ramaty spectral shape.
Conclusions: The
IGLED was revised to account for the variable GCR background. Integral
omnidirectional fluences reconstructed for most of GLE events were
added to IGLED. This forms the basis for more precise studies of
parameters of SEP events and thus for solar and space physics. The
revised fluences are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/640/A17
Title: The mini-neutron monitor: a new approach in neutron monitor
design
Authors: Strauss, Du Toit; Poluianov, Stepan; van der Merwe, Cobus;
Krüger, Hendrik; Diedericks, Corrie; Krüger, Helena; Usoskin,
Ilya; Heber, Bernd; Nndanganeni, Rendani; Blanco-Ávalos, Juanjo;
García-Tejedor, Ignacio; Herbst, Konstantin; Caballero-Lopez,
Rogelio; Moloto, Katlego; Lara, Alejandro; Walter, Michael; Giday,
Nigussie Mezgebe; Traversi, Rita
Bibcode: 2020JSWSC..10...39S
Altcode:
The near-Earth cosmic ray flux has been monitored for more than 70
years by a network of ground-based neutron monitors (NMs). With
the ever-increasing importance of quantifying the radiation risk
and effects of cosmic rays for, e.g., air and space-travel, it is
essential to continue operating the existing NM stations, while
expanding this crucial network. In this paper, we discuss a smaller
and cost-effective version of the traditional NM, the mini-NM. These
monitors can be deployed with ease, even to extremely remote locations,
where they operate in a semi-autonomous fashion. We believe that the
mini-NM, therefore, offers the opportunity to increase the sensitivity
and expand the coverage of the existing NM network, making this
network more suitable to near-real-time monitoring for space weather
applications. In this paper, we present the technical details of the
mini-NM's design and operation, and present a summary of the initial
tests and science results.
Title: Natural Sources of Ionization and Their Impact on Atmospheric
Electricity
Authors: Golubenko, K.; Rozanov, E.; Mironova, I.; Karagodin, A.;
Usoskin, I.
Bibcode: 2020GeoRL..4788619G
Altcode:
We present a study of atmospheric electricity using the
chemistry-climate model SOCOL considering ionization by solar energetic
particles during an extreme solar proton event (SPE), galactic cosmic
rays (GCR), and terrestrial radon (Rn-222). We calculate the global
distribution of the atmospheric conductivity and fair-weather downward
current density (Jz) using atmospheric ionization rates
from all sources. We found that Jz is enhanced (by more than
3.5 pA/m2) in radon source and polar regions. Contribution
of Rn-222 is essential at middle and low latitudes/altitudes where
GCR-induced air conductivity is reduced. The model results are in
good agreement with the available observations. We also studied the
effects of an extreme SPE, corresponding to the 774 AD event, on
the atmospheric electricity and found that it would lead to a large
increase of Jz on a global scale. The magnitude of the
effects depends on location and can exceed background value more than
30 times over the high latitudes (a conservative upper bound). Such
an assessment has been performed for the first time.
Title: VizieR Online Data Catalog: CR Ground Level Enhancements
spectra (IGLED) (Usoskin+, 2020)
Authors: Usoskin, I. G.; Koldobskiy, S.; Kovaltsov, G. A.; Gil, A.;
Usoskina, I.; Willamo, T.; Ibragimov, A.
Bibcode: 2020yCat..36400017U
Altcode:
Files (names as 'GLEXX_spec.dat') contain, for each GLE event numbered
as XX, name [Name], vertical geomagnetic cutoff rigidity [Pc], nominal
atmospheric depth [h], the integral GLE intensity [X], reconstructed
effective rigidity [Re] along with its full-range lower [e_Re] and upper
[E_Re] uncertainties, omni-directional integral fluence F(>Re)
[F] along with its full-range lower [eF] and upper [EF]
uncertainties, for all NMs with available data. F=0 implies that only
the upper limit on F(>Re) can be provided. (2 data files).
Title: Revisited Reference Solar Proton Event of 23 February 1956:
Assessment of the Cosmogenic-Isotope Method Sensitivity to Extreme
Solar Events
Authors: Usoskin, Ilya G.; Koldobskiy, Sergey A.; Kovaltsov, Gennady
A.; Rozanov, Eugene V.; Sukhodolov, Timofei V.; Mishev, Alexander L.;
Mironova, Irina A.
Bibcode: 2020JGRA..12527921U
Altcode: 2020arXiv200510597U
Our direct knowledge of solar eruptive events is limited to several
decades and does not include extreme events, which can only be studied
by the indirect proxy method over millennia, or by a large number
of Sun-like stars. There is a gap, spanning 1-2 orders of magnitude,
in the strength of events between directly observed and reconstructed
ones. Here, we study the proxy method sensitivity to identify extreme
solar particle events (SPEs). First, the strongest directly observed SPE
(23 February 1956), used as a reference for proxy-based reconstructions,
was revisited using the newly developed method. Next, sensitivity of
the cosmogenic-isotope method to detect a reference SPE was assessed
against the precision and number of individual isotopic records, showing
that it is too weak by a factor ≈30 to be reliably identified in a
single record. Uncertainties of 10Be and 14C data
are shown to be dominated by local/regional patterns and measurement
errors, respectively. By combining several proxy records, a SPE 4-5
times stronger than the reference one can be potentially detected,
increasing the present-day sensitivity by an order of magnitude. This
will allow filling the observational gap in SPE strength distribution,
thus enriching statistics of extreme events from 3-4 presently known
ones to several tens. This will provide a solid basis for research
in the field of extreme events, both for fundamental science, namely
solar and stellar physics, and practical applications, such as the
risk assessments of severe space-based hazards for modern technological
society.
Title: Current status and possible extension of the global neutron
monitor network
Authors: Mishev, Alexander; Usoskin, Ilya
Bibcode: 2020JSWSC..10...17M
Altcode: 2020arXiv200512621M
The global neutron monitor network has been successfully used over
several decades to study cosmic ray variations and fluxes of energetic
solar particles. Nowadays, it is used also for space weather purposes,
e.g. alerts and assessment of the exposure to radiation. Here, we
present the current status of the global neutron monitor network. We
discuss the ability of the global neutron monitor network to study
solar energetic particles, specifically during large ground level
enhancements. We demonstrate as an example, the derived solar proton
characteristics during ground level enhancements GLE #5 and the
resulting effective dose over the globe at a typical commercial jet
flight altitude of 40 kft (≈12,200 m) above sea level. We present
a plan for improvement of space weather services and applications of
the global neutron monitor network, specifically for studies related to
solar energetic particles, namely an extension of the existing network
with several new monitors. We discuss the ability of the optimized
global neutron monitor network to study various populations of solar
energetic particles and to provide reliable space weather services.
Title: Properties of Neon, Magnesium, and Silicon Primary Cosmic
Rays Results from the Alpha Magnetic Spectrometer
Authors: Aguilar, M.; Ali Cavasonza, L.; Ambrosi, G.; Arruda, L.;
Attig, N.; Barao, F.; Barrin, L.; Bartoloni, A.; Başeǧmez-du Pree,
S.; Battiston, R.; Becker, U.; Behlmann, M.; Beischer, B.; Berdugo,
J.; Bertucci, B.; Bindi, V.; de Boer, W.; Bollweg, K.; Borgia, B.;
Boschini, M. J.; Bourquin, M.; Bueno, E. F.; Burger, J.; Burger,
W. J.; Burmeister, S.; Cai, X. D.; Capell, M.; Casaus, J.; Castellini,
G.; Cervelli, F.; Chang, Y. H.; Chen, G. M.; Chen, H. S.; Chen, Y.;
Cheng, L.; Chou, H. Y.; Chouridou, S.; Choutko, V.; Chung, C. H.;
Clark, C.; Coignet, G.; Consolandi, C.; Contin, A.; Corti, C.; Cui,
Z.; Dadzie, K.; Dai, Y. M.; Delgado, C.; Della Torre, S.; Demirköz,
M. B.; Derome, L.; Di Falco, S.; Di Felice, V.; Díaz, C.; Dimiccoli,
F.; von Doetinchem, P.; Dong, F.; Donnini, F.; Duranti, M.; Egorov, A.;
Eline, A.; Feng, J.; Fiandrini, E.; Fisher, P.; Formato, V.; Freeman,
C.; Galaktionov, Y.; Gámez, C.; García-López, R. J.; Gargiulo, C.;
Gast, H.; Gebauer, I.; Gervasi, M.; Giovacchini, F.; Gómez-Coral,
D. M.; Gong, J.; Goy, C.; Grabski, V.; Grandi, D.; Graziani, M.;
Guo, K. H.; Haino, S.; Han, K. C.; Hashmani, R. K.; He, Z. H.; Heber,
B.; Hsieh, T. H.; Hu, J. Y.; Huang, Z. C.; Incagli, M.; Jang, W. Y.;
Jia, Yi; Jinchi, H.; Kanishev, K.; Khiali, B.; Kim, G. N.; Kirn, Th.;
Konyushikhin, M.; Kounina, O.; Kounine, A.; Koutsenko, V.; Kuhlman,
A.; Kulemzin, A.; La Vacca, G.; Laudi, E.; Laurenti, G.; Lazzizzera,
I.; Lebedev, A.; Lee, H. T.; Lee, S. C.; Li, J. Q.; Li, M.; Li, Q.;
Li, S.; Li, T. X.; Li, Z. H.; Light, C.; Lin, C. H.; Lippert, T.;
Liu, Z.; Lu, S. Q.; Lu, Y. S.; Luebelsmeyer, K.; Luo, J. Z.; Lyu,
S. S.; Machate, F.; Mañá, C.; Marín, J.; Marquardt, J.; Martin,
T.; Martínez, G.; Masi, N.; Maurin, D.; Menchaca-Rocha, A.; Meng,
Q.; Mo, D. C.; Molero, M.; Mott, P.; Mussolin, L.; Ni, J. Q.; Nikonov,
N.; Nozzoli, F.; Oliva, A.; Orcinha, M.; Palermo, M.; Palmonari, F.;
Paniccia, M.; Pashnin, A.; Pauluzzi, M.; Pensotti, S.; Phan, H. D.;
Piandani, R.; Plyaskin, V.; Poluianov, S.; Qi, X. M.; Qin, X.; Qu,
Z. Y.; Quadrani, L.; Rancoita, P. G.; Rapin, D.; Reina Conde, A.;
Rosier-Lees, S.; Rozhkov, A.; Rozza, D.; Sagdeev, R.; Schael, S.;
Schmidt, S. M.; Schulz von Dratzig, A.; Schwering, G.; Seo, E. S.;
Shan, B. S.; Shi, J. Y.; Siedenburg, T.; Solano, C.; Sonnabend,
R.; Song, J. W.; Sun, Q.; Sun, Z. T.; Tacconi, M.; Tang, X. W.;
Tang, Z. C.; Tian, J.; Ting, Samuel C. C.; Ting, S. M.; Tomassetti,
N.; Torsti, J.; Tüysüz, C.; Urban, T.; Usoskin, I.; Vagelli, V.;
Vainio, R.; Valente, E.; Valtonen, E.; Vázquez Acosta, M.; Vecchi, M.;
Velasco, M.; Vialle, J. P.; Wallmann, C.; Wang, L. Q.; Wang, N. H.;
Wang, Q. L.; Wang, S.; Wang, X.; Wang, Z. X.; Wei, J.; Weng, Z. L.;
Wu, H.; Xiong, R. Q.; Xu, W.; Yan, Q.; Yang, Y.; Yi, H.; Yu, Y. J.;
Yu, Z. Q.; Zannoni, M.; Zhang, C.; Zhang, F.; Zhang, F. Z.; Zhang,
J. H.; Zhang, Z.; Zhao, F.; Zheng, Z. M.; Zhuang, H. L.; Zhukov, V.;
Zichichi, A.; Zimmermann, N.; Zuccon, P.; AMS Collaboration
Bibcode: 2020PhRvL.124u1102A
Altcode:
We report the observation of new properties of primary cosmic rays, neon
(Ne), magnesium (Mg), and silicon (Si), measured in the rigidity range
2.15 GV to 3.0 TV with 1.8 ×106 Ne , 2.2 ×106
Mg , and 1.6 ×106 Si nuclei collected by the Alpha Magnetic
Spectrometer experiment on the International Space Station. The Ne and
Mg spectra have identical rigidity dependence above 3.65 GV. The three
spectra have identical rigidity dependence above 86.5 GV, deviate
from a single power law above 200 GV, and harden in an identical
way. Unexpectedly, above 86.5 GV the rigidity dependence of primary
cosmic rays Ne, Mg, and Si spectra is different from the rigidity
dependence of primary cosmic rays He, C, and O. This shows that the
Ne, Mg, and Si and He, C, and O are two different classes of primary
cosmic rays.
Title: Big Data Processing and Modeling in Solar Physics
Authors: Huang, X.; Usoskin, I.; Zhang, L. Y.; Wang, H. N.
Bibcode: 2020AdAst2020E...2H
Altcode:
No abstract at ADS
Title: Updated Neutron-Monitor Yield Function: Bridging Between In
Situ and Ground-Based Cosmic Ray Measurements
Authors: Mishev, Alexander L.; Koldobskiy, Sergey A.; Kovaltsov,
Gennady A.; Gil, Agnieszka; Usoskin, Ilya G.
Bibcode: 2020JGRA..12527433M
Altcode:
An updated yield function for a standard NM64 neutron monitor (NM)
is computed and extended to different atmospheric depths from sea
level to 500 g/cm2 (∼5.7 km altitude) and is presented
as lookup tables and a full parametrization. The yield function was
validated using the cosmic ray spectra directly measured in space by
the AMS-02 experiment during the period May 2011 through May 2017 and
confronted with count rates of all NM64-type NMs being in operation
during this period. Using this approach, stability of all the selected
NMs was analyzed for the period 2011-2017. Most of NMs appear very
stable and suitable for studies of long-term solar modulation of
cosmic rays. However, some NMs suffer from instabilities like trends,
apparent jumps, or strong seasonal waves in the count rates.
Title: Interplanetary Protons versus Interacting Protons in the 2017
September 10 Solar Eruptive Event
Authors: Kocharov, Leon; Pesce-Rollins, Melissa; Laitinen, Timo;
Mishev, Alexander; Kühl, Patrick; Klassen, Andreas; Jin, Meng;
Omodei, Nicola; Longo, Francesco; Webb, David F.; Cane, Hilary V.;
Heber, Bernd; Vainio, Rami; Usoskin, Ilya
Bibcode: 2020ApJ...890...13K
Altcode:
We analyze the relativistic proton emission from the Sun during the
eruptive event on 2017 September 10, which caused a ground-level
enhancement (GLE 72) registered by the worldwide network of
neutron monitors. Using the neutron monitor data and interplanetary
transport modeling both along and across interplanetary magnetic
field (IMF) lines, we deduce parameters of the proton injection into
the interplanetary medium. The inferred injection profile of the
interplanetary protons is compared with the profile of the >100 MeV
γ-ray emission observed by the Fermi Large Area Telescope, attributed
to pion production from the interaction of >300 MeV protons at
the Sun. GLE 72 started with a prompt component that arrived along
the IMF lines. This was followed by a more prolonged enhancement
caused by protons arriving at the Earth across the IMF lines from
the southwest. The interplanetary proton event is modeled using two
sources—one source at the root of the Earth-connected IMF line and
another source situated near the solar western limb. The maximum
phase of the second injection of interplanetary protons coincides
with the maximum phase of the prolonged >100 MeV γ-ray emission
that originated from a small area at the solar western limb, below the
current sheet trailing the associated coronal mass ejection (CME). A
possible common source of interacting protons and interplanetary
protons is discussed in terms of proton acceleration at the CME bow
shock versus coronal (re-)acceleration in the wake of the CME.
Title: Spectral characteristic of mid-term quasi-periodicities in
sunspot data
Authors: Frick, P.; Sokoloff, D.; Stepanov, R.; Pipin, V.; Usoskin, I.
Bibcode: 2020MNRAS.491.5572F
Altcode: 2019arXiv191106881F
Numerous analyses suggest the existence of various quasi-periodicities
in solar activity. The power spectrum of solar activity recorded
in sunspot data is dominated by the ∼11-yr quasi-periodicity,
known as the Schwabe cycle. In the mid-term range (1 month-11 yr)
a pronounced variability known as a quasi-biennial oscillation
is widely discussed. In the shorter time-scale a pronounced peak,
corresponding to the synodic solar rotation period (∼27 d), is
observed. Here we revisit the mid-term solar variability in terms of
statistical dynamics of fully turbulent systems, where solid arguments
are required to accept an isolated dominant frequency in a continuous
(smooth) spectrum. For this, we first undertook an unbiased analysis
of the standard solar data, sunspot numbers and the F10.7 solar radio
flux index, by applying a wavelet tool, which allows one to perform
a frequency-time analysis of the signal. Considering the spectral
dynamics of solar activity cycle by cycle, we showed that no single
periodicity can be separated, in a statistically significant manner,
in the specified range of periods. We examine whether a model of the
solar dynamo can reproduce the mid-term oscillation pattern observed
in solar data. We found that a realistically observed spectrum can be
explained if small spatial (but not temporal) scales are effectively
smoothed. This result is important because solar activity is a global
feature, although monitored via small-scale tracers like sunspots.
Title: What Can Be Learned from Modern Data?
Authors: Kusano, K.; Cliver, E.; Hayakawa, H.; Kovaltsov, G. A.;
Usoskin, I. G.
Bibcode: 2019esps.book....2K
Altcode:
Our detailed knowledge about the Sun comes from instrumental
observations, the precision and sophistication of which have rapidly
increased over the last decades. The primary focus of this book lies in
solar eruptive events. This chapter provides a review of what we know
about solar eruptive events, especially about the strongest observed
ones, from precise modern data.
Title: Cosmogenic Isotopes as Proxies for Solar Energetic Particles
Authors: Jull, T.; Baroni, M.; Feinberg, A.; Kovaltsov, G.; Mekhaldi,
F.; Muscheler, R.; Poluianov, S.; Rozanov, E.; Sukhodolov, T.; Usoskin,
I. G.
Bibcode: 2019esps.book....4J
Altcode:
Since the statistic of solar events based on direct observational data
is not sufficient to assess extreme events (see Chapter 2), indirect
proxy data needs to be used. The principles and details of the use
of cosmogenic isotopes as a proxy for solar energetic particles are
presented in this chapter.
Title: Extreme Solar Particle Storms; The hostile Sun
Authors: Miyake, Fusa; Usoskin, Ilya; Poluianov, Stepan
Bibcode: 2019esps.book.....M
Altcode:
It is becoming increasingly clear that our modern technological
society is vulnerable to the impacts of severe solar storms, radiation,
particle and geomagnetic disturbances. However, the potential severity
of these extreme solar events and their probability of occurring are
unknown. What can we expect from the Sun? What could the most severe
solar particle storms look like? Does the Sun have an unlimited ability
to produce severe storms? Can a destructive “black swan” event
occur? Direct solar data covers only several decades, a period too
short to answer these questions. Fortunately, other indirect ways to
study these possibly rare extreme solar storms have been discovered,
paving the way for analysis of these events on the multi-millennial
time scale. At present, studies of extreme solar events are growing,
forming a new research discipline. This book, written by leaders in
the corresponding aspects of the field, presents a first systematic
review of the current state of the art.
Title: Further Search for Extreme Events
Authors: Miyake, F.; Ebihara, Y.; Hayakawa, H.; Maehara, H.; Mitsuma,
Y.; Usoskin, I.; Wang, F.; Willis, D. M.
Bibcode: 2019esps.book....7M
Altcode:
Not all possible datasets about extreme solar events in the past
are explored currently; we are still at the beginning of a long
path. It is likely that more events can be identified in the past,
and the parameters of the found ones will be defined with higher
accuracy. Prospects for the further searches for extreme solar events
are summarized in this chapter.
Title: Introduction
Authors: Usoskin, I.; Miyake, F.
Bibcode: 2019esps.book....1U
Altcode:
This chapter introduces the concept of extreme solar events.
Title: Properties of Cosmic Helium Isotopes Measured by the Alpha
Magnetic Spectrometer
Authors: Aguilar, M.; Ali Cavasonza, L.; Ambrosi, G.; Arruda, L.;
Attig, N.; Bachlechner, A.; Barao, F.; Barrau, A.; Barrin, L.;
Bartoloni, A.; Başeǧmez-du Pree, S.; Battiston, R.; Becker, U.;
Behlmann, M.; Beischer, B.; Berdugo, J.; Bertucci, B.; Bindi, V.;
de Boer, W.; Bollweg, K.; Borgia, B.; Boschini, M. J.; Bourquin,
M.; Bueno, E. F.; Burger, J.; Burger, W. J.; Cai, X. D.; Capell,
M.; Caroff, S.; Casaus, J.; Castellini, G.; Cervelli, F.; Chang,
Y. H.; Chen, G. M.; Chen, H. S.; Chen, Y.; Cheng, L.; Chou, H. Y.;
Choutko, V.; Chung, C. H.; Clark, C.; Coignet, G.; Consolandi, C.;
Contin, A.; Corti, C.; Cui, Z.; Dadzie, K.; Dai, Y. M.; Datta, A.;
Delgado, C.; Della Torre, S.; Demirköz, M. B.; Derome, L.; Di Falco,
S.; Di Felice, V.; Díaz, C.; Dimiccoli, F.; von Doetinchem, P.;
Dong, F.; Donnini, F.; Duranti, M.; Egorov, A.; Eline, A.; Feng, J.;
Fiandrini, E.; Fisher, P.; Formato, V.; Galaktionov, Y.; Gámez, C.;
García-López, R. J.; Gargiulo, C.; Gast, H.; Gebauer, I.; Gervasi,
M.; Giovacchini, F.; Gómez-Coral, D. M.; Gong, J.; Goy, C.; Grabski,
V.; Grandi, D.; Graziani, M.; Guo, K. H.; Haino, S.; Han, K. C.; He,
Z. H.; Hsieh, T. H.; Huang, H.; Huang, Z. C.; Incagli, M.; Jang,
W. Y.; Jia, Yi; Jinchi, H.; Kanishev, K.; Khiali, B.; Kim, G. N.;
Kirn, Th.; Konyushikhin, M.; Kounina, O.; Kounine, A.; Koutsenko, V.;
Kulemzin, A.; La Vacca, G.; Laudi, E.; Laurenti, G.; Lazzizzera, I.;
Lebedev, A.; Lee, H. T.; Lee, S. C.; Li, J. Q.; Li, Q.; Li, T. X.;
Li, Z. H.; Light, C.; Lin, C. H.; Lippert, T.; Liu, Z.; Lu, S. Q.;
Lu, Y. S.; Luebelsmeyer, K.; Luo, F.; Luo, J. Z.; Luo, Xi; Lyu, S. S.;
Machate, F.; Mañá, C.; Marín, J.; Martin, T.; Martínez, G.; Masi,
N.; Maurin, D.; Menchaca-Rocha, A.; Meng, Q.; Mo, D. C.; Molero, M.;
Mott, P.; Mussolin, L.; Nelson, T.; Ni, J. Q.; Nikonov, N.; Nozzoli,
F.; Oliva, A.; Orcinha, M.; Palermo, M.; Palmonari, F.; Paniccia,
M.; Pashnin, A.; Pauluzzi, M.; Pensotti, S.; Phan, H. D.; Plyaskin,
V.; Poireau, V.; Poluianov, S.; Popkow, A.; Qi, X. M.; Qin, X.; Qu,
Z. Y.; Quadrani, L.; Rancoita, P. G.; Rapin, D.; Reina Conde, A.;
Rosier-Lees, S.; Rozhkov, A.; Rozza, D.; Sagdeev, R.; Schael, S.;
Schmidt, S. M.; Schulz von Dratzig, A.; Schwering, G.; Seo, E. S.;
Shan, B. S.; Shi, J. Y.; Siedenburg, T.; Solano, C.; Song, J. W.;
Sun, Z. T.; Tacconi, M.; Tang, X. W.; Tang, Z. C.; Tian, J.; Ting,
Samuel C. C.; Ting, S. M.; Tomassetti, N.; Torsti, J.; Tüysüz,
C.; Urban, T.; Usoskin, I.; Vagelli, V.; Vainio, R.; Valente, E.;
Valtonen, E.; Vázquez Acosta, M.; Vecchi, M.; Velasco, M.; Vialle,
J. P.; Wang, L. Q.; Wang, N. H.; Wang, Q. L.; Wang, X.; Wang, X. Q.;
Wang, Z. X.; Wei, J.; Weng, Z. L.; Wu, H.; Xiong, R. Q.; Xu, W.; Yan,
Q.; Yang, Y.; Yi, H.; Yu, Y. J.; Yu, Z. Q.; Zannoni, M.; Zeissler, S.;
Zhang, C.; Zhang, F.; Zhang, J. H.; Zhang, Z.; Zhao, F.; Zheng, Z. M.;
Zhuang, H. L.; Zhukov, V.; Zichichi, A.; Zimmermann, N.; Zuccon, P.;
AMS Collaboration
Bibcode: 2019PhRvL.123r1102A
Altcode:
Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the
International Space Station of 3He 44 fluxes are
presented. The measurements are based on 100 million 4He
nuclei in the rigidity range from 2.1 to 21 GV and 18 million
3He from 1.9 to 15 GV collected from May 2011 to November
2017. We observed that the 3He and 4He fluxes
exhibit nearly identical variations with time. The relative magnitude
of the variations decreases with increasing rigidity. The rigidity
dependence of the 3He/4He flux ratio is measured
for the first time. Below 4 GV, the 3He/4He flux
ratio was found to have a significant long-term time dependence. Above
4 GV, the 3He/4He flux ratio was found to be time
independent, and its rigidity dependence is well described by a single
power law ∝RΔ with Δ =-0.294 ±0.004 . Unexpectedly,
this value is in agreement with the B/O and B/C spectral indices at
high energies.
Title: New Method of Assessment of the Integral Fluence of Solar
Energetic (> 1 GV Rigidity) Particles from Neutron Monitor Data
Authors: Koldobskiy, Sergey A.; Kovaltsov, Gennady A.; Mishev,
Alexander L.; Usoskin, Ilya G.
Bibcode: 2019SoPh..294...94K
Altcode:
A new method to reconstruct the high-rigidity part (≥ 1 GV)
of the spectral fluence of solar energetic particles (SEP) for
GLE events, based on the world-wide neutron monitor (NM) network
data, is presented. The method is based on the effective rigidity
Reff and scaling factor Keff. In contrast to
many other methods based on derivation of the best-fit parameters
of a prescribed spectral shape, it provides a true non-parametric
(viz. free of a priori assumptions on the exact spectrum) estimate
of fluence. We reconstructed the SEP fluences for two recent GLE
events, #69 (20 Jan. 2005) and #71 (17 May 2012), using four NM yield
functions: (CD00 - Clem and Dorman in Space Sci. Rev.93, 335, 2000),
(CM12 - Caballero-Lopez and Moraal in J. Geophys. Res.117, A12103,
2012), (Mi13 - Mishev, Usoskin, and Kovaltsov in J. Geophys. Res.118,
2783, 2013), and (Ma16 - Mangeard et al. in J. Geophys. Res.121, 7435,
2016b). The results were compared with full reconstructions and direct
measurements by the PAMELA instrument. While reconstructions based on
Mi13 and CM12 yield functions are consistent with the measurements,
those based on CD00 and Ma16 ones underestimate the fluence by a factor
of 2 - 3. It is also shown that the often used power-law approximation
of the high-energy tail of SEP spectrum does not properly describe the
GLE spectrum in the NM-energy range. Therefore, the earlier estimates
of GLE integral fluences need to be revised.
Title: A neutron monitor as an integral spectrometer for GLE analysis:
Effective rigidity and reassessment of integral fluxes
Authors: Koldobskiy, S.; Mishev, A.; Kovaltsov, G.; Usoskin, I.
Bibcode: 2019ICRC...36.1093K
Altcode: 2019PoS...358.1093K
No abstract at ADS
Title: Usage of the global NM network for assessment of the radiation
exposure at flight altitudes
Authors: Mishev, A.; Usoskin, I.
Bibcode: 2019ICRC...36.1123M
Altcode: 2019PoS...358.1123M
No abstract at ADS
Title: Multi-NM spectral slope analysis of long-term cosmic-ray
variations at Earth
Authors: Usoskin, I.; Väisänen, P.; Mursula, K.
Bibcode: 2019ICRC...36.1165U
Altcode: 2019PoS...358.1165U
No abstract at ADS
Title: Cosmic-ray variability on the multi-millennial time scale:
A new multi-proxy reconstruction
Authors: Usoskin, I.; Wu, C. J.; Krivova, N.; Solanki, S. K.;
Kovaltsov, G.; Baroni, M.; Bard, E.
Bibcode: 2019ICRC...36.1164U
Altcode: 2019PoS...358.1164U
No abstract at ADS
Title: Validation of the neutron monitor yield functions using data
from AMS-02 and PAMELA experiments, 2006-2017
Authors: Koldobskiy, S.; Bindi, V.; Corti, C.; Kovaltsov, G.;
Usoskin, I.
Bibcode: 2019ICRC...36.1094K
Altcode: 2019PoS...358.1094K
No abstract at ADS
Title: Spectra of solar energetic particle and galactic cosmic rays
over a million years reconstructed using aluminium-26 data from
lunar rocks
Authors: Poluianov, S.; Kovaltsov, G.; Usoskin, I.
Bibcode: 2019ICRC...36.1139P
Altcode: 2019PoS...358.1139P
No abstract at ADS
Title: Neutron monitor yield function at several altitudes above
sea level: new improved computation
Authors: Mishev, A.; Kovaltsov, G.; Usoskin, I.
Bibcode: 2019ICRC...36.1125M
Altcode: 2019PoS...358.1125M
No abstract at ADS
Title: Spectra of extreme GLEs derived using neutron monitor network
records
Authors: Mishev, A.; Usoskin, I.
Bibcode: 2019ICRC...36.1124M
Altcode: 2019PoS...358.1124M
No abstract at ADS
Title: Historical astronomical data: urgent need for preservation,
digitization enabling scientific exploration
Authors: Pevtsov, Alexei; Griffin, Elizabeth; Grindlay, Jonathan;
Kafka, Stella; Bartlett, Jennifer; Usoskin, Ilya; Mursula, Kalevi;
Gibson, Sarah; Pillet, Valentín; Burkepile, Joan; Webb, David; Clette,
Frédéric; Hesser, James; Stetson, Peter; Muñoz-Jaramillo, Andres;
Hill, Frank; Bogart, Rick; Osborn, Wayne; Longcope, Dana
Bibcode: 2019BAAS...51c.190P
Altcode: 2019arXiv190304839P; 2019astro2020T.190P
This white paper emphasizes critical importance of preservation,
digitization and scientific exploration of historical astronomical
data. It outlines the rationale, provides examples of new science
with such data, and reviews the potential losses to science if nothing
it done.
Title: Normalization of the neutron monitor response to cosmic rays
using AMS-02 measurements
Authors: Usoskin, Ilya; Koldobsky, Sergey; Kovaltsov, Gennady
Bibcode: 2019EGUGA..21.4226U
Altcode:
A network of ground-based neutron monitors (NMs) is the main tool to
study cosmic ray variability on long-term scales. However, still there
is a systematic uncertainty related to the yield function of a NM to
cosmic ray variability, as several presently used yield functions offer
different results. Until recently, it was hardly possible to directly
verify and validate the NM yield functions, but the new measurements
of cosmic ray spectra by AMS-02 experiment give, for the first time,
such a possibility. Here we present a detailed analysis of the NM
data and AMS02-base spectra for the period May 2011 through May 2017,
and validate the existing yield functions. We show that the yield
function by Mishev et al. (2013) provides the results which yields the
best agreement with data. We also provide a new way to parameterize
contribution of heavier cosmic ray species (helium to iron) to NM
count rate.
Title: An analysis of the spectral properties of long-term galactic
cosmic ray variability in the heliosphere via a multiple-dataset study
Authors: Väisänen, Pauli; Usoskin, Ilya; Mursula, Kalevi
Bibcode: 2019EGUGA..2117690V
Altcode:
The heliosphere is formed by the open solar magnetic field and
solar wind flow, modulating galactic cosmic rays (GCR) from galactic
sources. Changes in the Sun and the heliosphere affect this solar
modulation of GCR. The most prominent type of variation in the Sun
is the 22-year solar cycle, caused by the Sun's magnetic activity
including changing polarity, which influences the path of the GCR in
the heliosphere. Other shorter- and longer-term variations are also
observable and affect processes in the heliosphere, the near-Earth
space and on Earth. These variations can also be identified from
the power spectral density (PSD) of GCR variability. Analysing the
PSD can also reveal information about the distribution of power
between different scales, observed as different power laws of the
spectrum. Earlier work has identified spectral peaks using data,
e.g., from neutron monitors. Less effort has been given to analyse
data from in-situ spacecraft. Spectral peaks observed at Earth
include, e.g., the 11-year solar cycle variation, the 1.75-year
midterm quasiperiodicity, the 155-day Rieger periodicity, the 27-day
solar rotational periodicity and the diurnal periodicity. Using high
quality long-term GCR data from instruments aboard various spacecraft
(such as CRIS on ACE, CRS on Voyager 1&2, and COSPIN on Ulysses)
and on Earth (neutron monitors), we extend the earlier Earth-based
studies to in-situ heliospheric data and compare and analyse the
spectral properties of GCR variability over long time scales. In
addition to changes in time, we also look at GCR variability across
different parts of the heliosphere. We identify spectral peaks and
calculate the spectral index for undisturbed frequency ranges. With
this comprehensive analysis, we can provide a reliable depiction of
the heliospheric GCR variation in time, which helps us understand the
process of solar modulation and the underlying space climate evolution.
Title: Validation of the Neutron Monitor Yield Function Using Data
From AMS-02 Experiment, 2011-2017
Authors: Koldobskiy, Sergey A.; Bindi, Veronica; Corti, Claudio;
Kovaltsov, Gennady A.; Usoskin, Ilya G.
Bibcode: 2019JGRA..124.2367K
Altcode: 2019arXiv190401929K
The newly published spectra of protons and helium over time directly
measured in space by the Alpha Magnetic Spectrometer (AMS-02)
experiment for the period 2011-2017 provide a unique opportunity to
calibrate ground-based neutron monitors (NMs). Here, calibration
of several stable sea level NMs (Inuvik, Apatity, Oulu, Newark,
Moscow, Hermanus, and Athens) was performed using these spectra. Four
modern NM yield functions were verified: Mi13 (Mishev et al., 2013, https://doi.org/10.1002/jgra.50325),
Ma16 (Mangeard et al., 2016, https://doi.org/10.1002/2016JA023515),
CM12 (Caballero-Lopez & Moraal, 2012, https://doi.org/10.1029/2012JA017794),
and CD00 (Clem & Dorman, 2000, https://doi.org/10.1023/A:1026508915269),
on the basis of the cosmic ray spectra measured by AMS-02. The Mi13
yield function was found to realistically represent the NM response
to galactic cosmic rays. CM12 yield function leads to a small skew
in the solar cycle dependence of the scaling factor. In contrast,
Ma16 and CD00 yield functions tend to overestimate the NM sensitivity
to low-rigidity (<10 GV) cosmic rays. This effect may be important
for an analysis of ground level enhancements, leading to a potential
underestimate of fluxes of solar energetic particles as based on NM
data. The Mi13 yield function is recommended for quantitative analyses
of NM data, especially for ground level enhancements. The validity of
the force field approximation was studied, and it was found that it
fits well the directly measured proton spectra, within a few percent
for periods of low to moderate activity and up to ≈10% for active
periods. The results of this work strengthen and validate the method
of the cosmic ray variability analysis based on the NM data and yield
function formalism and improve its accuracy.
Title: Long-Term and Solar Cycle Variation of Galactic Cosmic Rays:
Evidence for Variable Heliospheric Turbulence
Authors: Väisänen, Pauli; Usoskin, Ilya; Mursula, Kalevi
Bibcode: 2019JGRA..124..804V
Altcode:
The Sun modulates the flux of galactic cosmic rays (GCR) reaching the
Earth's orbit. GCR flux has been measured by ground-based neutron
monitors (NMs) for several decades, which provides an interesting
long-term monitor of solar activity and the heliospheric magnetic
field. Here we study the long-term evolution of the power spectrum
of GCR over the last six solar cycles, using the power law slope in
the frequency range 5.56·10-6 to 2.14·10-6 Hz
(between 50 and 130 hr). We use data from 31 neutron monitors during
1953-2016. We show that the power law slopes vary within the solar
cycle, with a Kolmogorov-type slope observed at solar minimum and a
random-walk-type slope observed at solar maximum. This implies that
the different conditions in the different phases of the solar cycle
affect the scaling properties of heliospheric turbulence and, thereby,
cosmic ray variability.
Title: Solar total and spectral irradiance reconstruction over the
last 9000 years
Authors: Wu, C. -J.; Krivova, N. A.; Solanki, S. K.; Usoskin, I. G.
Bibcode: 2018A&A...620A.120W
Altcode: 2018arXiv181103464W
Context. Changes in solar irradiance and in its spectral distribution
are among the main natural drivers of the climate on Earth. However,
irradiance measurements are only available for less than four decades,
while assessment of solar influence on Earth requires much longer
records.
Aims: The aim of this work is to provide the most
up-to-date physics-based reconstruction of the solar total and spectral
irradiance (TSI/SSI) over the last nine millennia.
Methods:
The concentrations of the cosmogenic isotopes 14C and
10Be in natural archives have been converted to decadally
averaged sunspot numbers through a chain of physics-based models. TSI
and SSI are reconstructed with an updated SATIRE model. Reconstructions
are carried out for each isotope record separately, as well as
for their composite.
Results: We present the first ever
SSI reconstruction over the last 9000 years from the individual
14C and 10Be records as well as from their
newest composite. The reconstruction employs physics-based models to
describe the involved processes at each step of the procedure.
Conclusions: Irradiance reconstructions based on two different
cosmogenic isotope records, those of 14C and 10Be,
agree well with each other in their long-term trends despite their
different geochemical paths in the atmosphere of Earth. Over the last
9000 years, the reconstructed secular variability in TSI is of the
order of 0.11%, or 1.5 W m-2. After the Maunder minimum,
the reconstruction from the cosmogenic isotopes is consistent with
that from the direct sunspot number observation. Furthermore, over
the nineteenth century, the agreement of irradiance reconstructions
using isotope records with the reconstruction from the sunspot number
by Chatzistergos et al. (2017, A&A, 602, A69) is better than that
with the reconstruction from the WDC-SILSO series (Clette et al. 2014,
Space Sci. Rev., 186, 35), with a lower χ2-value.
Title: An Anisotropic Cosmic-Ray Enhancement Event on 07-June-2015:
A Possible Origin
Authors: Gil, Agnieszka; Kovaltsov, Gennady A.; Mikhailov, Vladimir
V.; Mishev, Alexander; Poluianov, Stepan; Usoskin, Ilya G.
Bibcode: 2018SoPh..293..154G
Altcode:
A usual event, called anisotropic cosmic-ray enhancement (ACRE), was
observed as a small increase (≤5 % ) in the count rates of polar
neutron monitors during 12 - 19 UT on 07 June 2015. The enhancement
was highly anisotropic, as detected only by neutron monitors with
asymptotic directions in the southwest quadrant in geocentric solar
ecliptic (GSE) coordinates. The estimated rigidity of the corresponding
particles is ≤1 GV. No associated detectable increase was found in
the space-borne data from the Geostationary Operational Environmental
Satellite (GOES), the Energetic and Relativistic Nuclei and Electron
(ERNE) on board the Solar and Heliospheric Observatory (SOHO), or the
Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics
(PAMELA) instruments, whose sensitivity was not sufficient to detect
the event. No solar energetic particles were present during that time
interval. The heliospheric conditions were slightly disturbed, so
that the interplanetary magnetic field strength gradually increased
during the event, followed by an increase of the solar wind speed
after the event. It is proposed that the event was related to a
crossing of the boundary layer between two regions with different
heliospheric parameters, with a strong gradient of low-rigidity
(<1 GV) particles. It was apparently similar to another cosmic-ray
enhancement (e.g., on 22 June 2015) that is thought to have been caused
by the local anisotropy of Forbush decreases, with the difference that
in our case, the interplanetary disturbance was not observed at Earth,
but passed by southward for this event.
Title: Solar energetic particles and galactic cosmic rays over
millions of years as inferred from data on cosmogenic 26Al
in lunar samples
Authors: Poluianov, S.; Kovaltsov, G. A.; Usoskin, I. G.
Bibcode: 2018A&A...618A..96P
Altcode: 2018arXiv180710153P
Aims: Lunar soil and rocks are not protected by a magnetic
field or an atmosphere and are continuously irradiated by energetic
particles that can produce cosmogenic radioisotopes directly inside
rocks at different depths depending on the particle's energy. This
allows the mean fluxes of solar and galactic cosmic rays to be assessed
on the very long timescales of millions of years.
Methods: Here
we show that lunar rocks can serve as a very good particle integral
spectrometer in the energy range 20-80 MeV. We have developed a new
method based on precise modeling, that is applied to measurements
of 26Al (half-life ≈0.7 megayears) in lunar samples
from the Apollo mission, and present the first direct reconstruction
(i.e., without any a priori assumptions) of the mean energy spectrum of
solar and galactic energetic particles over a million of years.
Results: We show that the reconstructed spectrum of solar energetic
particles is totally consistent with that over the last decades,
despite the very different levels of solar modulation of galactic
cosmic rays (ϕ = 496 ± 40 MV over a million years versus (ϕ =
660 ± 20 MV for the modern epoch). We also estimated the occurrence
probability of extreme solar events and argue that no events with the
F(>30 MeV) fluence exceeding 5×1010 and 1011
cm-2 are expected on timescales of a thousand and million
years, respectively.
Conclusions: We conclude that the mean
flux of solar energetic particles hardly depends on the level of solar
activity, in contrast to the solar modulation of galactic cosmic
rays. This puts new observational constraints on solar physics and
becomes important for assessing radiation hazards for the planned
space missions.
Title: Neutron monitor count rate increase as a proxy for dose rate
assessment at aviation altitudes during GLEs
Authors: Mishev, Alexander; Tuohino, Sasu; Usoskin, Ilya
Bibcode: 2018JSWSC...8A..46M
Altcode:
Radiation exposure due to cosmic rays, specifically at cruising aviation
altitudes, is an important topic in the field of space weather. While
the effect of galactic cosmic rays can be easily assessed on the basis
of recent models, estimate of the dose rate during strong solar particle
events is rather complicated and time consuming. Here we compute the
maximum effective dose rates at a typical commercial flight altitude
of 35 kft (≈11 000 m above sea level) during ground level enhancement
events, where the necessary information, namely derived energy/rigidity
spectra of solar energetic particles, is available. The computations are
carried out using different reconstructions of the solar proton spectra,
available in bibliographic sources, leading to multiple results for
some events. The computations were performed employing a recent model
for effective dose and/or ambient dose equivalent due to cosmic ray
particles. A conservative approach for the computation was assumed. A
highly significant correlation between the maximum effective dose
rate and peak NM count rate increase during ground level enhancement
events is derived. Hence, we propose to use the peak NM count rate
increase as a proxy in order to assess the peak effective dose rate
at flight altitude during strong solar particle events using the real
time records of the worldwide global neutron monitor network.
Title: First Analysis of Ground-Level Enhancement (GLE) 72 on 10
September 2017: Spectral and Anisotropy Characteristics
Authors: Mishev, A.; Usoskin, I.; Raukunen, O.; Paassilta, M.;
Valtonen, E.; Kocharov, L.; Vainio, R.
Bibcode: 2018SoPh..293..136M
Altcode: 2018arXiv181010536M
Using data obtained with neutron monitors and space-borne instruments,
we analyzed the second ground-level enhancement (GLE) of Solar Cycle 24,
namely the event of 10 September 2017 (GLE 72), and derived the spectral
and angular characteristics of associated GLE particles. We employed
a new neutron-monitor yield function and a recently proposed model
based on an optimization procedure. The method consists of simulating
particle propagation in a model magnetosphere in order to derive the
cutoff rigidity and neutron-monitor asymptotic directions. Subsequently,
the rigidity spectrum and anisotropy of GLE particles are obtained
in their dynamical evolution during the event on the basis of an
inverse-problem solution. The derived angular distribution and spectra
are discussed briefly.
Title: Comment on the paper by Popova et al. "On a role of quadruple
component of magnetic field in defining solar activity in grand
cycles"
Authors: Usoskin, Ilya G.
Bibcode: 2018JASTP.176...69U
Altcode: 2017arXiv171005203U
The paper by Popova et al. presents an oversimplified mathematical
model of solar activity with a claim of predicting/postdicting it
for several millennia ahead/backwards. The work contains several
flaws devaluating the results: (1) the method is unreliable from the
point of view of signal processing (it is impossible to make harmonic
predictions for thousands of years based on only 35 years of data)
and lacks quality control; (2) the result of post-diction apparently
contradicts the observational data. (3) theoretical speculations
make little sense. To summarize, a multi-harmonic mathematical model,
hardly related to full solar dynamo theory, is presented, which is not
applicable to realistic solar conditions because of the significant
chaotic/stochastic intrinsic component and strong non-stationarity of
solar activity. The obtained result is apparently inconsistent with the
data in the past and thus cannot be trusted for the future predictions.
Title: Solar superstorm of AD 774 recorded subannually by Arctic
tree rings
Authors: Uusitalo, J.; Arppe, L.; Hackman, T.; Helama, S.; Kovaltsov,
G.; Mielikäinen, K.; Mäkinen, H.; Nöjd, P.; Palonen, V.; Usoskin,
I.; Oinonen, M.
Bibcode: 2018NatCo...9.3495U
Altcode:
Recently, a rapid increase in radiocarbon (14C) was observed
in Japanese tree rings at AD 774/775. Various explanations for the
anomaly have been offered, such as a supernova, a γ-ray burst,
a cometary impact, or an exceptionally large Solar Particle Event
(SPE). However, evidence of the origin and exact timing of the event
remains incomplete. In particular, a key issue of latitudinal dependence
of the 14C intensity has not been addressed yet. Here, we
show that the event was most likely caused by the Sun and occurred
during the spring of AD 774. Particularly, the event intensities
from various locations show a strong correlation with the latitude,
demonstrating a particle-induced 14C poleward increase,
in accord with the solar origin of the event. Furthermore, both annual
14C data and carbon cycle modelling, and separate earlywood
and latewood 14C measurements, confine the photosynthetic
carbon fixation to around the midsummer.
Title: Structure of the Power Spectral Density of Galactic Cosmic
Ray Variation during 1953-2016
Authors: Väisänen, Pauli; Usoskin, Ilya; Mursula, Kalevi
Bibcode: 2018IAUS..335...82V
Altcode:
Fluxes of galactic cosmic rays (GCR) observed at 1 AU are modulated
inside the heliosphere at different time scales. Here we study the
properties of the power spectral density (PSD) of galactic cosmic
ray variability using hourly data from 31 neutron monitors (NM)
from 1953 to 2016. We pay particular attention to the reliability of
the used datasets and methods. We present the overall PSD and discuss
different parts of the spectrum and the related periodicities. We find
significant spectral peaks at the periods of 11 years, 1.75 years,
155 days, 27 days and 24 hours and the harmonics of the latter two
peaks. We calculate a power law slope of -1.79 +/- 0.13 for the period
range between 50 and 130 hours and a slope of -1.34 +/- 0.17 for the
period range between 40 days and 3.4 years (1000 - 30000 h).
Title: Spatial Organization of Seven Extreme Solar Energetic
Particle Events
Authors: Kocharov, Leon; Pohjolainen, Silja; Reiner, Mike J.; Mishev,
Alexander; Wang, Haimin; Usoskin, Ilya; Vainio, Rami
Bibcode: 2018ApJ...862L..20K
Altcode:
Emission of relativistic protons and helium responsible for extreme
solar particle events (ground level enhancements (GLEs)) is often
structured. We investigate its organization depending on the eruption
stage characterized by the heliocentric height of associated coronal
mass ejections (CMEs). Seven GLEs are considered: events on 1997
November 6, 1998 May 2, 2000 July 14, 2001 December 26, 2003 November
2, 2006 December 13, and 2012 May 17, which are half of the SOlar
and Heliospheric Observatory (SOHO )-era GLEs, excluding very weak
events. Count-rate profiles of the GLEs plotted as a function of the CME
height reveal two types (or two components) of the high-energy particle
emission. The first component rises in a step-like manner during
the CME transit from 2 R ⊙ to 3 R ⊙, when
the CME exits from predominantly closed coronal magnetic structures,
irrespective of the CME speed (type H). This component is of coronal
origin. The second component of the GLE-producing particles starts to
rise when CME is at about 4 R ⊙, achieves its maximum at
6-10 R ⊙, and declines shortly after that (type J). The
type J particle injection into the interplanetary space coincides with
the decametric-hectometric radio burst complex that includes enhanced
emission of type II and concurrent low-frequency type III bursts,
indicative of the CME interaction with a streamer-like structure at
a few solar radii from the Sun. Those could be delayed particles
from the flare region. A possible additional contribution of the
CME-bow-shock acceleration in unstructured solar wind is not large in
the two considered types of events.
Title: Effective Rigidity of a Polar Neutron Monitor for Recording
Ground-Level Enhancements
Authors: Koldobskiy, Sergey A.; Kovaltsov, Gennady A.; Usoskin, Ilya G.
Bibcode: 2018SoPh..293..110K
Altcode:
The "effective" rigidity of a neutron monitor for a ground-level
enhancement (GLE) event is defined so that the event-integrated
fluence of solar energetic protons with rigidity above it is directly
proportional to the integral intensity of the GLE as recorded by a
polar neutron monitor, within a wide range of solar energetic-proton
spectra. This provides a direct way to assess the integral fluence
of a GLE event based solely on neutron-monitor data. The effective
rigidity/energy was found to be 1.13 - 1.42 GV (550 - 800 MeV). A
small model-dependent, systematic uncertainty in the value of the
effective rigidity is caused by uncertainties in the low-energy range
of the neutron-monitor yield function, which requires more detailed
computations of the latter.
Title: Upgrade of GLE database: Assessment of effective dose rate
at flight altitude
Authors: Tuohino, S.; Ibragimov, A.; Usoskin, I.; Mishev, A.
Bibcode: 2018AdSpR..62..398T
Altcode:
A new database for assessment of radiation doses at cruise
flight altitude in the Earth atmosphere, related to ground level
enhancement (GLE) events is created under VarSiTi/SCOSTEP support
and incorporated to the International ground level enhancement (GLE)
database (gle.oulu.fi). The upgraded database provides, for each GLE
event, where possible, information on the estimated energy/rigidity
spectra of solar energetic particles and the corresponding computed
effective doses at cruise flight altitude of 35 kft (10,668 m above
sea level). The computations are performed for various reconstructions
of solar energetic particles spectra, available in literature, thus
for some events there are several results. Computations were performed
using a recent model for assessment of effective dose due to cosmic ray
particles, applied specifically in the polar region, where the exposure
is maximal. This upgrade allows one to estimate the radiation effects at
cruise flight altitude caused by major GLE events over several decades.
Title: Solar Activity and Irradiance Reconstruction over the Holocene
Authors: Wu, Chi-Ju; Usoskin, Ilya; Krivova, Natalie; Solanki, Sami
K.; Kovaltsov, Gennady A.; Baroni, Melanie; Bard, Edouard
Bibcode: 2018cosp...42E3695W
Altcode:
Direct measurements of the solar irradiance are only available since
1978. To understand the solar influence on Earth's climate, longer
records and thus reconstructions of the solar variability in the past
are needed. The directly observed sunspot number allows going back
to 1610 A.D, although with progressively increasing uncertainty. To
assess solar variability at earlier times, one has to rely on indirect
proxies of solar activity, such as concentrations of cosmogenic isotopes
10Be and 14C in terrestrial archives. They are produced mostly in
the upper atmosphere by impinging galactic cosmic rays (GCRs). The
flux of GCRs is modulated by both the heliospheric magnetic field and
the geomagnetic field. Therefore, the isotope signals retrieved from
various sites around the globe show a very high degree of similarity,
reflecting changes in the solar activity. Still, short-and mid-term
deviations can be observed due to various systematic effects, such as
different geochemical production, atmospheric distribution processes
and local climatic conditions. To account for these differences, we
have constructed a state-of-the-art consistent multi-isotope composite
from one global 14C and six regional 10Be data sets. This composite is
then used to reconstruct decadal values of the total and spectral solar
irradiance over the Holocene with the semi-empirical SATIRE-M model,
while the quasi-11 year solar cycle has been simulated statistically.
Title: The effective energy for neutron monitors and cosmogenic
isotopes-redefined concept
Authors: Gil, Agnieszka; Usoskin, Ilya; Kovaltsov, Gennady A.;
Asvestari, Eleanna
Bibcode: 2018cosp...42E1207G
Altcode:
Cosmic ray variability is often described in terms of the modulation
potential (φ) changes. Based on measurements of ground-based
energy-integrating detectors, such as neutron monitors for the recent
decades, and by cosmogenic isotopes stored in natural archives for
the millennial timescale, variability of φ can be reconstructed. Here
we defined the effective energy of an energy-integrating detector as
energy at which the cosmic ray flux changeability is straightforward
proportional to that of the detector's response. We calculated that
the effective energy for the standard sea-level polar neutron monitor
is around 11-12 GeV/nucleon, while for cosmic ray reconstruction
based on cosmogenic isotopes it is around 6-7 GeV/nucleon and 5.5-6
GeV/nucleon for 14C data and 10Be, respectively. We compared results
based on different models of local interstellar spectrum (LIS) of
galactic cosmic rays, showing that the effective energy is determined
robustly against the particular LIS model.
Title: Solar activity over nine millennia: A consistent multi-proxy
reconstruction
Authors: Wu, C. J.; Usoskin, I. G.; Krivova, N.; Kovaltsov, G. A.;
Baroni, M.; Bard, E.; Solanki, S. K.
Bibcode: 2018A&A...615A..93W
Altcode: 2018arXiv180401302W
Aims: The solar activity in the past millennia can only
be reconstructed from cosmogenic radionuclide proxy records in
terrestrial archives. However, because of the diversity of the proxy
archives, it is difficult to build a homogeneous reconstruction. All
previous studies were based on individual, sometimes statistically
averaged, proxy datasets. Here we aim to provide a new consistent
multi-proxy reconstruction of the solar activity over the last 9000
yr, using all available long-span datasets of 10Be and
14C in terrestrial archives.
Methods: A new method,
based on a Bayesian approach, was applied for the first time to solar
activity reconstruction. A Monte Carlo search (using the χ2
statistic) for the most probable value of the modulation potential was
performed to match data from different datasets for a given time. This
provides a straightforward estimate of the related uncertainties. We
used six 10Be series of different lengths (from 500-10
000 yr) from Greenland and Antarctica, and the global 14C
production series. The 10Be series were resampled to match
wiggles related to the grand minima in the 14C reference
dataset. The stability of the long data series was tested.
Results: The Greenland Ice-core Project (GRIP) and the Antarctic EDML
(EPICA Dronning Maud Land) 10Be series diverge from each
other during the second half of the Holocene, while the 14C
series lies in between them. A likely reason for the discrepancy is the
insufficiently precise beryllium transport and deposition model for
Greenland, which leads to an undercorrection of the GRIP series for
the geomagnetic shielding effect. A slow 6-7 millennia variability
with lows at ca. 5500 BC and 1500 AD in the long-term evolution
of solar activity is found. Two components of solar activity can
be statistically distinguished: the main component, corresponding
to the "normal" moderate level, and a component corresponding to
grand minima. A possible existence of a component representing
grand maxima is indicated, but it cannot be separated from the main
component in a statistically significant manner.
Conclusions:
A new consistent reconstruction of solar activity over the last nine
millennia is presented with the most probable values of decadal sunspot
numbers and their realistic uncertainties. Independent components
of solar activity corresponding to the main moderate activity
and the grand-minimum state are identified; they may be related
to different operation modes of the dynamo. A table with the
reconstructed SN series is available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr(ftp://130.79.128.5)
or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/615/A93
Title: Extreme solar particle events: historical prospective
Authors: Usoskin, Ilya
Bibcode: 2018cosp...42E3472U
Altcode:
The era of space-borne or ground-based observations of solar energetic
particle events (SPEs) covers several decades, respectively. About 70
strong energetic events (ground-level enhancements, GLEs) have been
recorded by ground-based instrumentations, the greatest being GLE No.5
on 23-Feb-1956. However, the statistic is still insufficient to conclude
whether the Sun can produce stronger events, how much stronger and what
the expected rate of their occurrence can be. Of special importance
is the question of the worst-case scenario. In order to answer these
questions, one has to exploit data on much longer time scales, covering
millennia and millions of years, which can be done only using proxy
data of cosmogenic radionuclides. Here we present an brief overview
of the present state of the art in the study of extreme SEP events
and an assessment of the worst case scenario for the SEP fluence in
the vicinity of Earth.
Title: Revised historical solar irradiance forcing
Authors: Egorova, T.; Schmutz, W.; Rozanov, E.; Shapiro, A. I.;
Usoskin, I.; Beer, J.; Tagirov, R. V.; Peter, T.
Bibcode: 2018A&A...615A..85E
Altcode: 2018arXiv180400287E
Context. There is no consensus on the amplitude of historical solar
forcing. The estimated magnitude of the total solar irradiance (TSI)
difference between the Maunder minimum and the present time ranges
from 0.1 to 6 W m-2 making the simulation of the past and
future climate uncertain. One reason for this disagreement is the
applied evolution of the quiet Sun brightness in solar irradiance
reconstruction models. This work addresses the role of the quiet Sun
model choice and updated solar magnetic activity proxies on the solar
forcing reconstruction.
Aims: We aim to establish a plausible
range for the solar irradiance variability on decadal to millennial
timescales.
Methods: The spectral solar irradiance (SSI) is
calculated as a weighted sum of the contributions from sunspot umbra,
sunspot penumbra, faculae, and quiet Sun, which are pre-calculated with
the NLTE Spectral SYnthesis code (NESSY). We introduce activity belts
of the contributions from sunspots and faculae and a new structure
model for the quietest state of the Sun. We assume that the brightness
of the quiet Sun varies in time proportionally to the secular (22-yr
smoothed) variation of the solar modulation potential.
Results:
A new reconstruction of the TSI and SSI covering the period 6000 BCE -
2015 CE is presented. The model simulates solar irradiance variability
during the satellite era well. The TSI change between the Maunder and
recent minima ranges between 3.7 and 4.5 W m-2 depending
on the applied solar modulation potential. The implementation of
a new quietest Sun model reduces, by approximately a factor of two,
the relative solar forcing compared to the largest previous estimation,
while the application of an updated solar modulation potential increases
the forcing difference between the Maunder minimum and the present
by 25-40%.
Title: Global NM network - a usefull tool to assess radiation hazard
at flight altitudes
Authors: Mishev, Alexander; Usoskin, Ilya
Bibcode: 2018cosp...42E2299M
Altcode:
An important topic in the field of space weather is the assessment of
radiation exposure at commercial flight altitudes. A specific interest
is related to the contribution of solar energetic particles. For this
purpose a precise information about solar energetic particle (SEP)
characteristics, namely rigidity spectrum and angular distribution
is necessary. Direct measurements with space-borne instruments can
provide precise information of SEPs. However, they are constrained in
some cases, because the specifics of spacecraft orbits. On the other
hand ground based detectors, namely the global neutron monitor network
provides a continuous operation. SEP characteristics can be derived
using neutron monitor (NM) data during a special class of SEP events
- the ground level enhancements (GLEs). A precise analysis of SEP
spectral and angular characteristics using NM data requires several
steps: detailed computation of assymptotic cones and cut-off rigidity
of NMs used for the analysis, modeling of global NM network response
using NM yield function and optimization procedure in order to derive
spectral and angular characteristics of SEPs. Similar procedure with
modifications, namely simplification of the model is applied for
sub-GLEs analysis. Subsequently on the basis of the derived spectra
and angular characteristics and using recent model based on previously
computed yield functions we calculate the effective dose during the GLEs
and sub-GLEs at typical commercial flight altitude of 35 kft. Several
examples are shown. Hence, we demonstrated that the global NM network
is a useful tool to assess the radiation exposure of aircrew due to CR
of galactic and solar origin. In addition, we created a new database
for assessment of radiation doses in the Earth atmosphere, related
to GLE events created under VarSiTi/SCOSTEP support and incorporated
to the International GLE database. The upgraded database provides,
for each GLE event, where possible, information on the estimated SEP
energy/rigidity spectra, the corresponding computed effective doses
and bibliography. The effective dose rates were computed for altitude
of 35 kft in a polar region, where the exposure is maximal.
Title: An updated definition of GLE and sub-GLE events
Authors: Usoskin, Ilya; Shea, Margaret; Smart, Don; Poluianov, Stepan;
Mishev, Alexander
Bibcode: 2018cosp...42E3473U
Altcode:
The concept of the ground-level enhancement (GLE, http://gle.oulu.fi)
of the neutron monitor (NM) count rate, caused by solar energetic
particles (SEP), plays an important role for many statistical and
scientific studies. The classical definition says that a GLE has been
identified when a near simultaneous increase (typically associated with
solar activity) is registered by at least two differently located NMs
regardless of their atmospheric and geomagnetic cutoff properties. This
included NMs at a high-altitude polar site with the reduced total
cutoff (SOPO/B at the Amundsen-Scott station, South Pole, Antarctica,
elevation 2835 m asl), and Vostok NM (Vostok station, 3500 m, operating
only 1963-1969). However, a new high-altitude polar NM (DOMC/B)
was installed at Concordia station (Dome C, Antarctica, elevation
3233 m asl) in 2015. As a result, there is a pair of exceptionally
sensitive instruments (SOPO/B and DOMC/B) that can formally register
a near simultaneous increase from a relatively weak SEP event below
the full atmospheric cutoff, which would have not been detected at
any other NM station and, accordingly, not accepted as a GLE before
2015. This would potentially distort the homogeneity of the present
GLE list by more frequent detections due to the enhanced sensitivity
of the global NM network.In order to maintain the homogeneity of the
events previously listed as ground-level enhancements, we propose to
modify the presently used GLE definition as follows: ``A GLE event
is registered when there are near-time coincident and statistically
significant enhancements of the count rates of at least two differently
located neutron monitors, including at least one neutron monitor near
sea level and a corresponding enhancement in the proton flux measured
by a space-borne instrument(s).'' We also propose to classify SEP
events under the full atmospheric cutoff, which are seen only in data
of high-altitude polar NMs, as sub-GLEs. We note that this definition
does not affect the present list of GLEs.
Title: GLE 72 on 10 September 2017 - an analysis using neutron
monitor and space-borne data
Authors: Mishev, Alexander; Usoskin, Ilya; Valtonen, Eino; Kocharov,
Leon; Vainio, Rami; Raukunen, Osku; Paassilta, Miikka
Bibcode: 2018cosp...42E2298M
Altcode:
The first ten days of September 2017 were characterized by intense
solar activity, producing several X-class flares and coronal mass
ejections (CMEs). The second ground level enhancement (GLE) event of
solar cycle 24, namely GLE 72 on 10 September 2017, was related to a
X8.2 solar flare. The flare peaked at 16:06 UT, leading to a gradual
solar energetic particle event measured by spacecraft up to proton
energies exceeding 700 MeV and to a very fast CME erupting over the
west limb. The GLE onset was observed by several neutron monitor
(NM) stations at about 16:15 UT (FSMT and INVK). However, a clearly
distinguishable signal, which allows one to derive the spectral
and angular characteristics of SEPs with sufficient precision, was
observed at 16:30 UT. The strongest increases were observed at the
DOMC/DOMB 10-15 %, SOPO/SOPB 5-8 % and FSMT 6%, above the pre-increase
levels. The event was characterized by a typical gradual increase. Here
we perform a precise analysis of spectral and angular features
of solar energetic particles (SEPs) on the basis of NM data. The
method includes several consequitive steps: detailed computation of
assymptotic cones and cut-off rigidity of each NM station used in
the analysis, an initial guess of the inverse problem by assuming
the apparent source position in a convenient way, application of the
NM yield function for detector response modelling and optimization
procedure in order to derive spectral and angular characteristics
of SEPs. In this study we use the Planetocosmics code and realistic
magnetospheric models for computations of assymptotic directions and
rigidity cut-offs. Here we present results from analysis of GLE 72,
namely SEP spectra and pitch angle distributions, which are obtained
in their dynamical development throughout the event. An interpretation
of the derived findings is performed.
Title: Variation of the PSD slopes of cosmic rays in 1953-2016
Authors: Väisänen, Pauli; Usoskin, Ilya; Mursula, Kalevi
Bibcode: 2018cosp...42E3483V
Altcode:
The flux of cosmic rays observed at the Earth is modulated by the
Sun and the heliosphere. Modulation of the galactic cosmic rays
(GCR) is mostly caused by scattering on the inhomogeneities of the
heliospheric magnetic field (HMF). Sporadic solar events like coronal
mass ejections and merged interaction regions affect the HMF and scatter
GCR. Turbulent variations are another source of inhomogeneities of the,
causing scattering at different scales. The variability of the cosmic
ray flux as measured ground-based neutron monitors (NMs) can serve as a
probe for heliospheric turbulence and its scaling. Turbulent phenomena
are often characterized by a power-law type power spectral density (PSD)
of the measured variable. Using 1-hour resolution data from the global
NM network in 1953-2016, we have studied the power-law slope in the
frequency range between 5.56*10^{-6} and 2.14*10^{-6} Hz, corresponding
to time scales of 50 and 130 hours. The mean power-law slope was found
to be -1.81±0.02. We have studied the temporal variation of this
power-law slope and found that the slope values differ for different
solar cycles and different cycle phases, with steeper slopes observed
usually during the ascending and maximum phases, and less steep slopes
during the declining and minimum phases. This implies that the scaling
of HMF turbulence varies in the course of the solar cycle, reflecting
different physical processes affecting GCR modulation.
Title: A Solar Cycle of Cosmic Ray Fluxes for 2006-2014: Comparison
between PAMELA and Neutron Monitors
Authors: Koldobskiy, Sergey A.; Kovaltsov, Gennady A.; Usoskin, Ilya G.
Bibcode: 2018JGRA..123.4479K
Altcode:
A comparison of cosmic proton spectra directly measured by the Payload
for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA)
experiment during 2006-2014 with data of polar neutron monitors for the
same time interval is presented. It is shown that the measured spectra
are well described by the force-field model for the modulation potential
range 350-750 MV. The obtained modulation potential agrees with that
calculated from the data of the world neutron monitor network for low
solar activity between 2006 and 2012 but diverges during the maximum
of solar cycle. The empirical relation between the modulation potential
and the (inverted) neutron monitor count rate appears somewhat steeper
than the modeled one, as confirmed also by data from fragmentary
balloon-borne measurements. A reason for the discrepancy is unclear
and calls for additional study using independent data sets.
Title: Long-term evolution of the power-law spectrum of galactic
cosmic rays in 1953-2016
Authors: Väisänen, Pauli; Usoskin, Ilya; Mursula, Kalevi
Bibcode: 2018EGUGA..20.6021V
Altcode:
The power spectrum of galactic cosmic ray (GCR) variability is
modulated by the heliospheric magnetic field and solar wind. The GCR
power spectrum consists of a number of important peaks (related e.g.,
to solar cycle, solar rotation and diurnal variation) and the background
power-law spectrum. The slope of the background power-law spectrum is
often used as a quantitative indicator of energy scaling of the signal,
indicating chaotic or stochastic behaviour like turbulence or Brownian
motion. We present a study of the statistical properties and long-term
evolution of the power-law slope of the spectral density of cosmic
rays calculated from 31 neutron monitors covering the time period from
1953 to 2016. We limit here the analysis of the slope to within the
time scales of 50 to 130 hours (frequency range 5.56*10-6 to 2.14*10-6
Hz), where the power spectrum has the most perfect power-law behaviour
outside the main spectral peaks. The mean power-law slope was found to
be -1.81. We studied the slopes in different phases of the solar cycle,
and found that they vary systematically within the solar cycle. Higher
(less steep) slopes of around -1.67 (corresponding to the Kolmogorov
spectrum) were observed during solar minima and steeper slopes of
around -2 (corresponding to random processes) during solar maxima.
Title: Extreme Solar Particle Storms: How hostile can the Sun be?
Authors: Usoskin, Ilya
Bibcode: 2018EGUGA..20.4306U
Altcode:
It is recognized now that strong sporadic events (called solar particle
storms) with high fluxes of solar energetic particles (SEP) produced
during eruptive solar flares and coronal mass ejections form a serious
issue for Space Weather and pose deadly hazards for technological
devices and even human lives outside the protective Earth's atmosphere
and magnetosphere. The strongest directly observed solar particle storm
took place on 23-Feb-1956 with a 50-x enhancement over the galactic
background as recorded on the ground. Can stronger storms appear? How
often? Can we assess the "worst case scenario"? Knowing answers to
these questions is of great importance, not only purely academic but
also societal and technological. The era of direct measurements of SEP
events by space-borne detectors covers 40-50 years, and by ground-based
instruments about 70 years. Because of the limited dataset we possess,
these questions can be answered only using indirect methods. An overview
of different method is presented here with a search for extreme SEP
events. First we discuss the method of cosmogenic radionuclides (14C,
10Be, 36Cl) measured in independently dateable natural archives,
that forms a reliable proxy of cosmic ray variability on the
centennial-millennial time scale. So far, three extreme SEP events
have been identified during the Holocene: the strongest known event of
775 AD, which was a factor 40-50 stronger than that of 23-Feb-1956,
and a couple of slightly weaker event of 994 AD an 3372 BC. Next we
discuss the method of cosmogenic isotopes (primarily 26Al) measured
in lunar rocks, which does not allow to identify individual events but
provides evaluation of the mean flux of SEP over a million of years. We
also critically discuss a statistical study of the large ensemble of
sun-like stars, some of which exhibit super-flares. Considering all
data in their diversity and recent achievements in this field, we
argue that the event of 775 AD may serve as the worst case scenario
of an extreme solar particle storm, and that we do not expect much
stronger events on the megayear timescale.
Title: Effective Energy of Neutron Monitors and Cosmogenic Isotopes
Authors: Gil, Agnieszka; Asvestari, Eleanna; Kovaltsov, Gennady;
Usoskin, Ilya
Bibcode: 2018EGUGA..2010485G
Altcode:
Galactic cosmic ray variations are often quantified with the aid of the
modulation potential (φ). For more than sixty years φ is typically
computed using measurements of ground-based energy-integrating
detectors, such as neutron monitors, and for the millennial scale
by cosmogenic isotopes stored in natural archives. Here we redefine
the effective energy of a detector, considering it as the energy
at which the cosmic ray flux variability is straightforwardly
proportional to that of the detector's count rate. We found that for
the standard sea-level polar neutron monitor the effective energy
is 11-12 GeV/nucleon, for cosmic ray reconstruction based on 14C
data 6-7 GeV/nucleon and for 10Be data 5.5-6 GeV/nucleon. We present
results based on various models of local interstellar spectrum (LIS)
of galactic cosmic rays, showing that the effective energy is defined
robustly against exact LIS model.
Title: Effective energy of solar energetic particles causing a
ground-level enhancement
Authors: Koldobsky, Sergey; Kovaltsov, Gennady; Usoskin, Ilya
Bibcode: 2018EGUGA..20.4376K
Altcode:
Ground level enhancements (GLEs) are short sporadic events when the
count rate of a ground-based neutron monitor (NM) is significantly
enhanced over the background of galactic cosmic rays due to high
fluxes of solar energetic particles (SEPs). It is difficult to measure
the spectrum of SEPs directly, since the measurements should be
performed outside the shielding effect of the Earth magnetosphere and
atmosphere. On the other hand, a quick estimate of the total fluence of
SEP above some effective energy Eeff can be made based on the observed
GLE response. Here we define such effective energy that the SEP fluence
above it is directly proportional to the GLE strength as recorded by
polar NMs. We show, using data from the International GLE database
(http://gle.oulu.fi) and applying a recent yield function of NM that
the response of a polar NM to a GLE is directly proportional to the
SEP fluence above 600-800 MeV. Thus, the effective energy of SEP as
detected by ground-based NMs is Eeff=600-880 MeV.
Title: A Test of the Active-Day Fraction Method of Sunspot Group
Number Calibration: Dependence on the Level of Solar Activity
Authors: Willamo, T.; Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2018SoPh..293...69W
Altcode: 2018arXiv180310501W
The method of active-day fraction (ADF) was proposed recently
to calibrate different solar observers to standard observational
conditions. The result of the calibration may depend on the overall
level of solar activity during the observational period. This dependency
is studied quantitatively using data of the Royal Greenwich Observatory
by formally calibrating synthetic pseudo-observers to the full reference
dataset. It is shown that the sunspot group number is precisely
estimated by the ADF method for periods of moderate activity, may
be slightly underestimated by 0.5 - 1.5 groups (≤10 % ) for strong
and very strong activity, and is strongly overestimated by up to 2.5
groups (≤30 % ) for weak-to-moderate activity. The ADF method becomes
inapplicable for the periods of grand minima of activity. In general,
the ADF method tends to overestimate the overall level of activity
and to reduce the long-term trends.
Title: VizieR Online Data Catalog: Reconstructed decadal sunspot
numbers (Wu+, 2018)
Authors: Wu, C. J.; Usoskin, I. G.; Krivova, N.; Kovaltsov, G. A.;
Baroni, M.; Bard, E.; Solanki, S. K.
Bibcode: 2018yCat..36150093W
Altcode:
The file contains the decadal numbers of sunspot groups including
the decade central year [Y], the low [Sl], the mean [SM]
and the upper [S_u] 1-sigma (68% bounds). (1 data file).
Title: Extreme Value Theory Applied to the Millennial Sunspot
Number Series
Authors: Acero, F. J.; Gallego, M. C.; García, J. A.; Usoskin, I. G.;
Vaquero, J. M.
Bibcode: 2018ApJ...853...80A
Altcode: 2018arXiv180109776A
In this work, we use two decadal sunspot number series reconstructed
from cosmogenic radionuclide data (14C in tree trunks, SN
14C, and 10Be in polar ice, SN 10Be) and the extreme value
theory to study variability of solar activity during the last nine
millennia. The peaks-over-threshold technique was used to compute, in
particular, the shape parameter of the generalized Pareto distribution
for different thresholds. Its negative value implies an upper bound
of the extreme SN 10Be and SN 14C timeseries. The return level for
1000 and 10,000 years were estimated leading to values lower than
the maximum observed values, expected for the 1000 year, but not for
the 10,000 year return levels, for both series. A comparison of these
results with those obtained using the observed sunspot numbers from
telescopic observations during the last four centuries suggests that
the main characteristics of solar activity have already been recorded
in the telescopic period (from 1610 to nowadays) which covers the full
range of solar variability from a Grand minimum to a Grand maximum.
Title: Can Superflares Occur on the Sun? A View from Dynamo Theory
Authors: Katsova, M. M.; Kitchatinov, L. L.; Livshits, M. A.; Moss,
D. L.; Sokoloff, D. D.; Usoskin, I. G.
Bibcode: 2018ARep...62...72K
Altcode: 2017arXiv171000015K
Recent data from the Kepler mission has revealed the occurrence
of superflares in Sun-like stars which exceed by far any observed
solar flares in released energy. Radionuclide data do not provide
evidence for occurrence of superflares on the Sun over the past eleven
millennia. Stellar data for a subgroup of superflaring Kepler stars are
analysed in an attempt to find possible progenitors of their abnormal
magnetic activity. A natural idea is that the dynamo mechanism in
superflaring stars differs in some respect from that in the Sun. We
search for a difference in the dynamo-related parameters between
superflaring stars and the Sun to suggest a dynamo mechanism as close
as possible to the conventional solar/stellar dynamo but capable of
providing much higher magnetic energy. Dynamo based on joint action of
differential rotation and mirror asymmetric motions can in principle
result in excitation of two types of magnetic fields. First of all,
it is well-known in solar physics dynamo waves. The point is that
another magnetic configuration with initial growth and further
stabilisation can also be excited. For comparable conditions,
magnetic field of second configuration is much stronger than that
of the first one just because dynamo does not spend its energy for
periodic magnetic field inversions but uses it for magnetic field
growth. We analysed available data from the Kepler mission concerning
the superflaring stars in order to find tracers of anomalous magnetic
activity. As suggested in a recent paper [1], we find that anti-solar
differential rotation or anti-solar sign of the mirror-asymmetry of
stellar convection can provide the desired strong magnetic field in
dynamo models. We confirm this concept by numerical models of stellar
dynamos with corresponding governing parameters. We conclude that the
proposed mechanism can plausibly explain the superflaring events at
least for some cool stars, including binaries, subgiants and, possibly,
low-mass stars and young rapid rotators.
Title: Solar Spectral Irradiance Reconstruction over 9 Millennia
from a Composite 14C and 10Be Series
Authors: Wu, C. J.; Usoskin, I. G.; Krivova, N.; Kovaltsov, G.;
Solanki, S. K.
Bibcode: 2017AGUFMSH42A..03W
Altcode:
The Sun is the main external energy source to the Earth and thus the
knowledge of solar variability on different time scales is important
for understanding the solar influence on the terrestrial atmosphere
and climate. The overall energy input and its spectral distribution
are described by the total (TSI) and spectral (SSI) solar irradiance,
respectively. Direct measurements of the solar irradiance provide
information on solar variability on the decadal and shorter time
scales, while the sunspot number record covers four centuries. On
yet longer time scales only indirect proxies can be used, such
as the concentrations of the cosmogenic isotopes 10Be and 14C in
terrestrial archives. These isotopes are produced in the terrestrial
atmosphere by impinging cosmic rays, whose flux is modulated by solar
activity. Therefore the isotope data retrieved from various natural
archives around the globe show a very high degree of similarity
reflecting changes in the solar activity. Nevertheless, significant
short-term deviations can be observed due to the different geochemical
production processes and local climatic conditions. We will present
the newest TSI/SSI reconstruction over the last 9000 years based
on a new consistent composite multi-isotope proxy series. The solar
irradiance reconstruction reveals the global and robust pattern of
solar variability in the past.
Title: The Maunder minimum and the Little Ice Age: an update from
recent reconstructions and climate simulations
Authors: Owens, Mathew J.; Lockwood, Mike; Hawkins, Ed; Usoskin,
Ilya; Jones, Gareth S.; Barnard, Luke; Schurer, Andrew; Fasullo, John
Bibcode: 2017JSWSC...7A..33O
Altcode:
The Maunder minimum (MM) was a period of extremely low solar activity
from approximately AD 1650 to 1715. In the solar physics literature, the
MM is sometimes associated with a period of cooler global temperatures,
referred to as the Little Ice Age (LIA), and thus taken as compelling
evidence of a large, direct solar influence on climate. In this
study, we bring together existing simulation and observational
studies, particularly the most recent solar activity and paleoclimate
reconstructions, to examine this relation. Using northern hemisphere
surface air temperature reconstructions, the LIA can be most readily
defined as an approximately 480 year period spanning AD 1440-1920,
although not all of this period was notably cold. While the MM occurred
within the much longer LIA period, the timing of the features are
not suggestive of causation and should not, in isolation, be used
as evidence of significant solar forcing of climate. Climate model
simulations suggest multiple factors, particularly volcanic activity,
were crucial for causing the cooler temperatures in the northern
hemisphere during the LIA. A reduction in total solar irradiance likely
contributed to the LIA at a level comparable to changing land use.
Title: GLE and Sub-GLE Redefinition in the Light of High-Altitude
Polar Neutron Monitors
Authors: Poluianov, S. V.; Usoskin, I. G.; Mishev, A. L.; Shea, M. A.;
Smart, D. F.
Bibcode: 2017SoPh..292..176P
Altcode: 2017arXiv171106161P
The conventional definition of ground-level enhancement (GLE) events
requires a detection of solar energetic particles (SEP) by at least two
differently located neutron monitors. Some places are exceptionally
well suitable for ground-based detection of SEP - high-elevation
polar regions with negligible geomagnetic and reduced atmospheric
energy/rigidity cutoffs. At present, there are two neutron-monitor
stations in such locations on the Antarctic plateau: SOPO/SOPB (at
Amundsen-Scott station, 2835 m elevation), and DOMC/DOMB (at Concordia
station, 3233 m elevation). Since 2015, when the DOMC/DOMB station
started continuous operation, a relatively weak SEP event that was
not detected by sea-level neutron-monitor stations was registered
by both SOPO/SOPB and DOMC/DOMB, and it was accordingly classified
as a GLE. This would lead to a distortion of the homogeneity of the
historic GLE list and the corresponding statistics. To address this
issue, we propose to modify the GLE definition so that it maintains
the homogeneity: A GLE event is registered when there are near-time
coincident and statistically significant enhancements of the count rates
of at least two differently located neutron monitors, including at least
one neutron monitor near sea level and a corresponding enhancement in
the proton flux measured by a space-borne instrument(s). Relatively weak
SEP events registered only by high-altitude polar neutron monitors,
but with no response from cosmic-ray stations at sea level, can be
classified as sub-GLEs.
Title: Assessment of spectral and angular characteristics of sub-GLE
events using the global neutron monitor network
Authors: Mishev, Alexander; Poluianov, Stepan; Usoskin, Ilya
Bibcode: 2017JSWSC...7A..28M
Altcode:
New recently installed high-altitude polar neutron monitors (NMs)
have made the worldwide NM network more sensitive to strong solar
energetic particle (SEP) events, registered at ground level, namely
ground-level enhancement (GLE) events. The DOMC/B and South Pole NMs in
addition to marginal cut-off rigidity also possess lower atmospheric
cut-off compared to the sea level. As a result, the two high-altitude
polar NM stations are able to detect lower energy SEP events, which
most likely would not be registered by the other (near sea level)
NMs. Here, we consider several candidates for such type of events
called sub-GLEs. Using the worldwide NM database (NMDB) records and
an optimization procedure combined with simulation of the global NM
network response, we assess the spectral and angular characteristics
of sub-GLE particles. With the estimated spectral characteristics as
an input, we evaluate the effective dose rate in polar and sub-polar
regions at typical commercial flight altitude. Hence, we demonstrate
that the global NM network is a useful tool to estimate important
space weather effects, e.g., the aircrew exposure due to cosmic rays
of galactic and/or solar origins.
Title: Neutron Monitors and Cosmogenic Isotopes as Cosmic Ray
Energy-Integration Detectors: Effective Yield Functions, Effective
Energy, and Its Dependence on the Local Interstellar Spectrum
Authors: Asvestari, Eleanna; Gil, Agnieszka; Kovaltsov, Gennady A.;
Usoskin, Ilya G.
Bibcode: 2017JGRA..122.9790A
Altcode:
The method of assessment of galactic cosmic rays (GCR) variability over
different timescales, using energy-integrating ground-based detectors
such as a neutron monitor and cosmogenic isotopes 10Be
and 14C stored in natural archives is revisited here. The
effective yield functions for cosmogenic 14C (globally
mixed in the atmosphere) and 10Be (realistically deposited
in the polar region) are calculated and provided, in a tabulated form,
in the supporting information. The effective energy of a detector is
redefined so that the variability of the flux of GCR particles at this
energy is equal to that of the detector's count rate. The effective
energy is found as 11-12 GeV/nucleon for the standard polar neutron
monitor, and 6-7 GeV/nucleon and 5.5-6 GeV/nucleon for 14C
and 10Be, respectively. New "calibration" relations between
the force-field modulation potentials, based on different models of
local interstellar spectra (LIS) are provided. While such relations
are typically based on refitting the modeled cosmic ray spectra with
a prescribed LIS model, the method introduced here straightforwardly
accounts for the exact type of the detector used to assess the
spectrum. The relations are given separately for ground-based neutron
monitors and cosmogenic isotopes. This work allows for harmonization
of different works related to variability of galactic cosmic ray flux
in the vicinity of Earth, on long-term scale.
Title: Analysis of Ground Level Enhancements (GLE): Extreme solar
energetic particle events have hard spectra
Authors: Asvestari, E.; Willamo, T.; Gil, A.; Usoskin, I. G.;
Kovaltsov, G. A.; Mikhailov, V. V.; Mayorov, A.
Bibcode: 2017AdSpR..60..781A
Altcode: 2016arXiv161202446A
Nearly 70 Ground Level Enhancements (GLEs) of cosmic rays have
been recorded by the worldwide neutron monitor network since the
1950s depicting a big variety of energy spectra of solar energetic
particles (SEP). Here we studied a statistical relation between
the event-integrated intensity of GLEs (calculated as count-rate
relative excess, averaged over all available polar neutron monitors,
and expressed in percent-hours) and the hardness of the solar
particle energy spectra. For each event the integral omnidirectional
event-integrated fluences of particles with energy above 30 MeV
(F30) and above 200 MeV (F200) were computed using
the reconstructed spectra, and the ratio between the two fluences was
considered as a simple index of the event's hardness. We also provided a
justification of the spectrum estimate in the form of the Band-function,
using direct PAMELA data for GLE 71 (17-May-2012). We found that, while
there is no clear relation between the intensity and the hardness for
weak events, all strong events with the intensity greater 100 %∗h
are characterized by a very hard spectrum. This implies that a hard
spectrum can be securely assumed for all extreme GLE events, e.g.,
those studied using cosmogenic isotope data in the past.
Title: New reconstruction of the sunspot group numbers since 1739
using direct calibration and "backbone" methods
Authors: Chatzistergos, Theodosios; Usoskin, Ilya G.; Kovaltsov,
Gennady A.; Krivova, Natalie A.; Solanki, Sami K.
Bibcode: 2017A&A...602A..69C
Altcode: 2017arXiv170206183C
Context. The group sunspot number (GSN) series constitute the longest
instrumental astronomical database providing information on solar
activity. This database is a compilation of observations by many
individual observers, and their inter-calibration has usually been
performed using linear rescaling. There are multiple published series
that show different long-term trends for solar activity.
Aims:
We aim at producing a GSN series, with a non-linear non-parametric
calibration. The only underlying assumptions are that the differences
between the various series are due to different acuity thresholds
of the observers, and that the threshold of each observer remains
constant throughout the observing period.
Methods: We used a
daisy chain process with backbone (BB) observers and calibrated all
overlapping observers to them. We performed the calibration of each
individual observer with a probability distribution function (PDF)
matrix constructed considering all daily values for the overlapping
period with the BB. The calibration of the BBs was carried out in a
similar manner. The final series was constructed by merging different
BB series. We modelled the propagation of errors straightforwardly
with Monte Carlo simulations. A potential bias due to the selection
of BBs was investigated and the effect was shown to lie within the 1σ
interval of the produced series. The exact selection of the reference
period was shown to have a rather small effect on our calibration
as well.
Results: The final series extends back to 1739 and
includes data from 314 observers. This series suggests moderate
activity during the 18th and 19th century, which is significantly
lower than the high level of solar activity predicted by other recent
reconstructions applying linear regressions.
Conclusions:
The new series provides a robust reconstruction, based on modern and
non-parametric methods, of sunspot group numbers since 1739, and it
confirms the existence of the modern grand maximum of solar activity in
the second half of the 20th century. Values of the group sunspot
number series are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/602/A69
Title: Updated sunspot group number reconstruction for 1749-1996
using the active day fraction method
Authors: Willamo, T.; Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2017A&A...601A.109W
Altcode: 2017arXiv170505109W
Aims: Sunspot number series are composed from observations of
hundreds of different observers that require careful normalization to
standard conditions. Here we present a new normalized series of the
number of sunspot groups for the period 1749-1996.
Methods:
The reconstruction is based on the active day fraction (ADF) method,
which is slightly updated with respect to previous works, and a revised
database of sunspot group observations.
Results: Stability of
some key solar observers has been evaluated against the composite
series. The Royal Greenwich Observatory dataset appears relatively
stable since the 1890s but is approximately 10% too low before that. A
declining trend of 10-15% in the quality of Wolfer's observations
is found between the 1880s and 1920s, suggesting that using him as
the reference observer may lead to additional uncertainties. Wolf
(small telescope) appears relatively stable between the 1860s and
1890s, without any obvious trend. The new reconstruction reflects
the centennial variability of solar activity as evaluated using the
singular spectrum analysis method. It depicts a highly significant
feature of the modern grand maximum of solar activity in the second
half of the 20th century, being a factor 1.33-1.77 higher than during
the 18 and 19th centuries.
Conclusions: The new series of
the sunspot group numbers with monthly and annual resolution is
provided forming a basis for new studies of the solar variability
and solar dynamo for the last 250 yr. Monthly values of the
reconstructed sunspot are available at the CDS via anonymous ftp to
http://cdsarc.u-strasbg.fr
(http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/601/A109
Title: Assessment of different sunspot number series using the
cosmogenic isotope 44Ti in meteorites
Authors: Asvestari, Eleanna; Usoskin, Ilya G.; Kovaltsov, Gennady A.;
Owens, Mathew J.; Krivova, Natalie A.; Rubinetti, Sara; Taricco, Carla
Bibcode: 2017MNRAS.467.1608A
Altcode: 2017MNRAS.tmp..193A
Many sunspot number series exist suggesting different levels of
solar activity during the past centuries. Their reliability can be
assessed only by comparing them with alternative indirect proxies. We
test different sunspot number series against the updated record of
cosmogenic radionuclide 44Ti measured in meteorites. Two
bounding scenarios of solar activity changes have been considered:
the HH-scenario (based on the series by Svalgaard and Schatten), in
particular, predicting moderate activity during the Maunder minimum,
and the LL-scenario (based on the RG series by Lockwood et
al.) predicting moderate activity for the 18th-19th centuries and the
very low activity level for the Maunder minimum. For each scenario,
the magnetic open solar flux, the heliospheric modulation potential and
the expected production of 44Ti were computed. The calculated
production rates were compared with the corresponding measurements of
44Ti activity in stony meteorites fallen since 1766. The
analysis reveals that the LL-scenario is fully consistent with the
measured 44Ti data, in particular, recovering the observed
secular trend between the 17th century and the Modern grand maximum. On
the contrary, the HH-scenario appears significantly inconsistent with
the data, mostly due to the moderate level of activity during the
Maunder minimum. It is concluded that the HH-scenario sunspot number
reconstruction significantly overestimates solar activity prior to the
mid-18th century, especially during the Maunder minimum. The exact level
of solar activity after 1750 cannot be distinguished with this method,
since both H- and L- scenarios appear statistically consistent with
the data.
Title: Investigating the Origins of Two Extreme Solar Particle Events:
Proton Source Profile and Associated Electromagnetic Emissions
Authors: Kocharov, Leon; Pohjolainen, Silja; Mishev, Alexander; Reiner,
Mike J.; Lee, Jeongwoo; Laitinen, Timo; Didkovsky, Leonid V.; Pizzo,
Victor J.; Kim, Roksoon; Klassen, Andreas; Karlicky, Marian; Cho,
Kyung-Suk; Gary, Dale E.; Usoskin, Ilya; Valtonen, Eino; Vainio, Rami
Bibcode: 2017ApJ...839...79K
Altcode:
We analyze the high-energy particle emission from the Sun in two
extreme solar particle events in which protons are accelerated to
relativistic energies and can cause a significant signal even in the
ground-based particle detectors. Analysis of a relativistic proton event
is based on modeling of the particle transport and interaction, from a
near-Sun source through the solar wind and the Earth’s magnetosphere
and atmosphere to a detector on the ground. This allows us to deduce
the time profile of the proton source at the Sun and compare it with
observed electromagnetic emissions. The 1998 May 2 event is associated
with a flare and a coronal mass ejection (CME), which were well
observed by the Nançay Radioheliograph, thus the images of the radio
sources are available. For the 2003 November 2 event, the low corona
images of the CME liftoff obtained at the Mauna Loa Solar Observatory
are available. Those complementary data sets are analyzed jointly
with the broadband dynamic radio spectra, EUV images, and other data
available for both events. We find a common scenario for both eruptions,
including the flare’s dual impulsive phase, the CME-launch-associated
decimetric-continuum burst, and the late, low-frequency type III
radio bursts at the time of the relativistic proton injection into
the interplanetary medium. The analysis supports the idea that the
two considered events start with emission of relativistic protons
previously accelerated during the flare and CME launch, then trapped
in large-scale magnetic loops and later released by the expanding CME.
Title: Heliospheric modulation of cosmic rays during the neutron
monitor era: Calibration using PAMELA data for 2006-2010
Authors: Usoskin, Ilya G.; Gil, Agnieszka; Kovaltsov, Gennady A.;
Mishev, Alexander L.; Mikhailov, Vladimir V.
Bibcode: 2017JGRA..122.3875U
Altcode: 2017arXiv170507197U
A new reconstruction of the heliospheric modulation potential for
galactic cosmic rays is presented for the neutron monitor era, since
1951. The new reconstruction is based on an updated methodology
in comparison to previous reconstructions: (1) the use of the
new-generation neutron monitor yield function; (2) the use of the
new model of the local interstellar spectrum, employing in particular
direct data from the distant missions; and (3) the calibration of the
neutron monitor responses to direct measurements of the cosmic ray
spectrum performed by the Payload for Antimatter Matter Exploration and
Light-nuclei Astrophysics (PAMELA) spaceborne spectrometer over 47 time
intervals during 2006-2010. The reconstruction is based on data from six
standard NM64-type neutron monitors (Apatity, Inuvik, Kergulen, Moscow,
Newark, and Oulu) since 1965 and two International Geophysical Year-type
ground-based detectors (Climax and Mount Washington) for 1951-1964. The
new reconstruction, along with the estimated uncertainties is tabulated
in the paper. The presented series forms a benchmark record of the
cosmic ray variability (in the energy range between 1 and 30 GeV) for
the last 60 years and can be used in long-term studies in the fields
of solar, heliospheric, and solar-terrestrial physics.
Title: A history of solar activity over millennia
Authors: Usoskin, Ilya G.
Bibcode: 2017LRSP...14....3U
Altcode:
Presented here is a review of present knowledge of the long-term
behavior of solar activity on a multi-millennial timescale, as
reconstructed using the indirect proxy method. The concept of solar
activity is discussed along with an overview of the special indices
used to quantify different aspects of variable solar activity, with
special emphasis upon sunspot number. Over long timescales, quantitative
information about past solar activity can only be obtained using a
method based upon indirect proxies, such as the cosmogenic isotopes
^{14}C and ^{10}Be in natural stratified archives (e.g., tree rings
or ice cores). We give an historical overview of the development of
the proxy-based method for past solar-activity reconstruction over
millennia, as well as a description of the modern state. Special
attention is paid to the verification and cross-calibration of
reconstructions. It is argued that this method of cosmogenic isotopes
makes a solid basis for studies of solar variability in the past on a
long timescale (centuries to millennia) during the Holocene. A separate
section is devoted to reconstructions of strong solar energetic-particle
(SEP) events in the past, that suggest that the present-day average
SEP flux is broadly consistent with estimates on longer timescales,
and that the occurrence of extra-strong events is unlikely. Finally,
the main features of the long-term evolution of solar magnetic activity,
including the statistics of grand minima and maxima occurrence, are
summarized and their possible implications, especially for solar/stellar
dynamo theory, are discussed.
Title: VizieR Online Data Catalog: Monthly numbers of sunspot groups
1749-1996 (Usoskin+, 2017)
Authors: Usoskin, I. G.; Gallet, Y.; Lopes, F.; Kovaltsov, G. A.;
Hulot, G.; Willamo, T.; Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2017yCat..36010109U
Altcode:
The file contain the monthly numbers of sunspot groups including the
fractional year [Y], the Mean value [GM], the low [Gl]
and upper [G_u] 1-sigma (68% bounds). (1 data file).
Title: VizieR Online Data Catalog: Monthly numbers of sunspot groups
1749-1996 (Willamo+, 2017)
Authors: Willamo, T.; Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2017yCat..36010109W
Altcode:
The file contain the monthly numbers of sunspot groups including the
fractional year [Y], the Mean value [GM], the low [Gl]
and upper [G_u] 1-sigma (68% bounds). (1 data file).
Title: Wings of the butterfly: Sunspot groups for 1826-2015
Authors: Leussu, R.; Usoskin, I. G.; Senthamizh Pavai, V.; Diercke,
A.; Arlt, R.; Denker, C.; Mursula, K.
Bibcode: 2017A&A...599A.131L
Altcode:
The spatio-temporal evolution of sunspot activity, the so-called Maunder
butterfly diagram, has been continously available since 1874 using
data from the Royal Greenwich Observatory, extended by SOON network
data after 1976. Here we present a new extended butterfly diagram
of sunspot group occurrence since 1826, using the recently digitized
data from Schwabe (1826-1867) and Spörer (1866-1880). The wings of
the diagram are separated using a recently developed method based
on an analysis of long gaps in sunspot group occurrence in different
latitude bands. We define characteristic latitudes, corresponding to
the start, end, and the largest extent of the wings (the F, L, and
H latitudes). The H latitudes (30°-45°) are highly significantly
correlated with the strength of the wings (quantified by the total sum
of the monthly numbers of sunspot groups). The F latitudes (20°-30°)
depict a weak tendency, especially in the southern hemisphere, to follow
the wing strength. The L latitudes (2°-10°) show no clear relation to
the wing strength. Overall, stronger cycle wings tend to start at higher
latitudes and have a greater wing extent. A strong (5-6)-cycle periodic
oscillation is found in the start and end times of the wings and in the
overlap and gaps between successive wings of one hemisphere. While the
average wing overlap is zero in the southern hemisphere, it is two to
three months in the north. A marginally significant oscillation of about
ten solar cycles is found in the asymmetry of the L latitudes. The new
long database of butterfly wings provides new observational constraints
to solar dynamo models that discuss the spatio-temporal distribution
of sunspot occurrence over the solar cycle and longer. Digital
data for Fig. 1 are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/599/A131
Title: VizieR Online Data Catalog: Group sunspot number series since
1739 (Chatzistergos+, 2017)
Authors: Chatzistergos, T.; Usoskin, I. G.; Kovaltsov, G. A.; Krivova,
N. A.; Solanki, S. K.
Bibcode: 2017yCat..36020069C
Altcode:
Annual, monthly, and daily values of the Group sunspot number series
produced in the paper. (3 data files).
Title: Analysis of Ground-Level Enhancements: Strong events are hard
Authors: Usoskin, I.; Asvestari, E.; Willamo, T.; Gil, A.; Kovaltsov,
G.; Mikhailov, V.; Mayorov, A.
Bibcode: 2017ICRC...35..126U
Altcode: 2017PoS...301..126U
No abstract at ADS
Title: Cosmogenic isotopes Be-7, Be-10, C-14, Na-22 and Cl-36 in
the atmosphere: Altitudinal profiles of yield functions
Authors: Poluianov, S.; Kovaltsov, G.; Mishev, A.; Usoskin, I.
Bibcode: 2017ICRC...35..124P
Altcode: 2017PoS...301..124P
No abstract at ADS
Title: Origin of two extreme solar particle events
Authors: Mishev, A.; Kocharov, L.; Pohjolainen, S.; Reiner, M. J.;
Lee, J.; Laitinen, T.; Didkovsky, L. V.; Pizzo, V. J.; Kim, R.;
Klassen, A.; Karlicky, M.; Choj, K. S.; Kovaltsov, G. A.; Usoskin,
I. G.; Valtonen, E.; Vainio, R.
Bibcode: 2017ICRC...35..146M
Altcode: 2017PoS...301..146M
No abstract at ADS
Title: Revisited definition of GLE
Authors: Poluianov, S.; Usoskin, I.; Mishev, A.; Smart, D. F.; Shea,
M. A.
Bibcode: 2017ICRC...35..125P
Altcode: 2017PoS...301..125P
No abstract at ADS
Title: Extreme solar particle events: Can we assess the worst case
scenario?
Authors: Usoskin, I.
Bibcode: 2017ICRC...35..127U
Altcode: 2017PoS...301..127U
No abstract at ADS
Title: The energetic particle intensity estimated from cosmogenic
isotope Al-26 produced in lunar samples
Authors: Poluianov, S.; Kovaltsov, G.; Usoskin, I.
Bibcode: 2017ICRC...35..123P
Altcode: 2017PoS...301..123P
No abstract at ADS
Title: Heliospheric modulation of galactic cosmic rays: Effective
energy of ground-based detectors
Authors: Gil, A.; Asvestari, E.; Kovaltsov, G.; Usoskin, I.
Bibcode: 2017ICRC...35...32G
Altcode: 2017PoS...301...32G
No abstract at ADS
Title: Computation of electron precipitation atmospheric ionization:
updated model CRAC-EPII
Authors: Mishev, A.; Artamonov, A.; Kovaltsov, G.; Mironova, I.;
Usoskin, I.
Bibcode: 2017ICRC...35...86M
Altcode: 2017PoS...301...86M
No abstract at ADS
Title: Updated model CRAC:HEPII of atmospheric ionization due to
high energy protons
Authors: Mishev, A.; Artamonov, A.; Kovalstov, G.; Usoskin, I.
Bibcode: 2017ICRC...35...79M
Altcode: 2017PoS...301...79M
No abstract at ADS
Title: An Optical Atmospheric Phenomenon Observed in 1670 over the
City of Astrakhan Was Not a Mid-Latitude Aurora
Authors: Usoskin, I. G.; Kovaltsov, G. A.; Mishina, L. N.; Sokoloff,
D. D.; Vaquero, J.
Bibcode: 2017SoPh..292...15U
Altcode: 2016arXiv161200705U
It has recently been claimed (Zolotova and Ponyavin Solar Phys., 291,
2869, 2016; ZP16 henceforth) that a mid-latitude optical phenomenon,
which took place over the city of Astrakhan in July 1670, according to
Russian chronicles, were a strong aurora borealis. If this were true,
it would imply a very strong or even severe geomagnetic storm during
the quietest part of the Maunder minimum. However, as we argue in this
article, this conclusion is erroneous and caused by a misinterpretation
of the chronicle record. As a result of a thorough analysis of the
chronicle text, we show that the described phenomenon occurred during
the daylight period of the day ("the last morning hour"), in the
south ("towards noon"), and its description does not match that of an
aurora. The date of the event was also interpreted incorrectly. We
conclude that this phenomenon was not a mid-latitude aurora, but an
atmospheric phenomenon, the so-called sundog (or parhelion), which is
a particular type of solar halo. Accordingly, the claim of a strong
mid-latitude aurora during the deep Maunder Minimum is not correct
and should be dismissed.
Title: Using global neutron monitor network data for GLE analysis:
recent results
Authors: Mishev, A.; Usoskin, I.; Kocharov, L.
Bibcode: 2017ICRC...35..147M
Altcode: 2017PoS...301..147M
No abstract at ADS
Title: Dependence of the Sunspot-Group Size on the Level of Solar
Activity and its Influence on the Calibration of Solar Observers
Authors: Usoskin, I. G.; Kovaltsov, G. A.; Chatzistergos, T.
Bibcode: 2016SoPh..291.3793U
Altcode: 2016SoPh..tmp..181U; 2016arXiv160900569U
We study the distribution of the sunspot-group size (area) and its
dependence on the level of solar activity. We show that the fraction
of small groups is not constant but decreases with the level of
solar activity so that high solar activity is mainly defined by
large groups. We analyze the possible influence of solar activity
on the ability of a realistic observer to see and report the daily
number of sunspot groups. It is shown that the relation between the
number of sunspot groups as seen by different observers with different
observational acuity thresholds is strongly nonlinear and cannot be
approximated by the traditionally used linear scaling (k -factors). The
observational acuity threshold [Ath] is considered to
quantify the quality of each observer, instead of the traditional
relative k -factor. A nonlinear c -factor based on Ath is
proposed, which can be used to correct each observer to the reference
conditions. The method is tested on a pair of principal solar observers,
Wolf and Wolfer, and it is shown that the traditional linear correction,
with the constant k -factor of 1.66 to scale Wolf to Wolfer, leads to
an overestimate of solar activity around solar maxima.
Title: Solar Total and Spectral Irradiance Reconstruction over Last
9000 Years
Authors: Wu, C. J.; Krivova, N.; Solanki, S. K.; Usoskin, I. G.
Bibcode: 2016AGUFMSA51B2430W
Altcode:
Although the mechanisms of solar influence on Earth climate system
are not yet fully understood, solar total and spectral irradiance are
considered to be among the main determinants. Solar total irradiance
is the total flux of solar radiative energy entering Earth's climate
system, whereas the spectral irradiance describes this energy is
distributed over the spectrum. Solar irradiance in the UV band is of
special importance since it governs chemical processes in the middle and
upper atmosphere. On timescales of the 11-year solar cycle and shorter,
solar irradiance is measured by space-based instruments while models
are needed to reconstruct solar irradiance on longer timescale. The
SATIRE-M model (Spectral And Total Irradiance Reconstruction over
millennia) is employed in this study to reconstruct solar irradiance
from decadal radionuclide isotope data such as 14C and 10Be stored in
tree rings and ice cores, respectively. A reconstruction over the last
9000 years will be presented.
Title: Non-linear re-calibration of group sunspot number series back
to 1819
Authors: Chatzistergos, T.; Usoskin, I. G.; Kovaltsov, G.; Solanki,
S. K.; Krivova, N.
Bibcode: 2016AGUFMSH31B2547C
Altcode:
Sunspot numbers form the longest series of direct observations
that give information about the activity of the Sun. It consists in
numerous records from different observers with different instruments
and techniques, and unavoidably requires a calibration of individual
observers to a standard reference condition. Such calibrations pose a
challenge and are still a subject of debate. Most of the calibration
methods are based on a simple linear scaling of data from one observer
to the other, proposed in the mid-19th century by Rudolf Wolf. This
method is still used in many recent reconstructions. However, this
linear method is shown, on both real and synthetic data, to be
very rough and incorrect because of the essentially non-linearity
of the relation.Here we present a new reconstruction of the
group sunspot number series back to 1819 attempting to take into
account the non-linearity of the relation between data of different
observers. We use an approach incorporating several overlapping backbone
observers (similar to Svalgaard and Schatten, 2016) and perform the
straightforward non-linear calibration of each observer to the backbone
(and the backbones with each other) based on the actual statistics of
the common daily values.
Title: Application of a full chain analysis using neutron monitor
data for space weather studies
Authors: Mishev, A.; Usoskin, I.
Bibcode: 2016arXiv161207043M
Altcode:
An important topic in the field of space weather is the precise
assessment of the contribution of galactic cosmic rays and solar
energetic particles on air crew exposure, specifically during eruptive
events on the Sun. Here we present a model, a full chain analysis based
on ground based measurements of cosmic rays with neutron monitors,
subsequent derivation of particle spectral and angular characteristics
and computation of dose rate. The model uses method for ground level
enhancement analysis and newly numerically computed yield functions
for conversion of secondary particle fluence to effective dose and/or
the ambient dose equivalent. The precise an adequate information
about the solar energetic particle spectra (SEPs) is the basis of the
model. Since SEPs possess an essential isotropic part, specifically
during the event onset, the angular characteristics should be also
derived with good precision. This can be achieved using neutron
monitor data during a special class of SEP events the ground level
enhancements (GLEs). On the basis of the method representing a sequence
of consecutive steps: computation of the NM asymptotic cones, NM
rigidity cut-off and application of convenient optimization procedure,
we derive the rigidity spectra and anisotropy characteristics of GLE
particles. For the computation we use newly computed yield function of
the standard sea-level 6NM64 neutron monitor for primary proton and
alpha CR nuclei as well as 6NM64 yield function at altitudes ranging
from the sea level up to 5000 m above the sea level. We derive the SEP
spectra and pitch angle distributions in their dynamical development
throughout the event. Subsequently on the basis of the derived spectra
and angular characteristics and previously computed yield functions
we calculate the effective dose and/or ambient dose equivalent during
the GLE. Several examples are shown.
Title: Tests of Sunspot Number Sequences: 2. Using Geomagnetic and
Auroral Data
Authors: Lockwood, M.; Owens, M. J.; Barnard, L.; Scott, C. J.;
Usoskin, I. G.; Nevanlinna, H.
Bibcode: 2016SoPh..291.2811L
Altcode: 2016SoPh..tmp...96L; 2016arXiv160501948L
We compare four sunspot-number data sequences against geomagnetic
and terrestrial auroral observations. The comparisons are made
for the original Solar Influences Data Center (SIDC) composite of
Wolf/Zürich/International sunspot number [RISNv1],
the group sunspot number [RG] by Hoyt and Schatten
(Solar Phys. 181, 491, 1998), the new "backbone" group sunspot
number [RBB] by Svalgaard and Schatten (Solar Phys.,
DOI, 2016), and the "corrected" sunspot number [RC] by
Lockwood, Owens, and Barnard (J. Geophys. Res. 119, 5172, 2014a). Each
sunspot number is fitted with terrestrial observations, or parameters
derived from terrestrial observations to be linearly proportional
to sunspot number, over a 30-year calibration interval of 1982 -
2012. The fits are then used to compute test sequences, which extend
further back in time and which are compared to RISNv1,
RG, RBB, and RC. To study the long-term
trends, comparisons are made using averages over whole solar cycles
(minimum-to-minimum). The test variations are generated in four ways:
i) using the IDV(1d) and IDV geomagnetic indices (for 1845 - 2013)
fitted over the calibration interval using the various sunspot numbers
and the phase of the solar cycle; ii) from the open solar flux (OSF)
generated for 1845 - 2013 from four pairings of geomagnetic indices by
Lockwood et al. (Ann. Geophys. 32, 383, 2014a) and analysed using the
OSF continuity model of Solanki, Schüssler, and Fligge (Nature, 408,
445, 2000), which employs a constant fractional OSF loss rate; iii)
the same OSF data analysed using the OSF continuity model of Owens and
Lockwood (J. Geophys. Res. 117, A04102, 2012), in which the fractional
loss rate varies with the tilt of the heliospheric current sheet and
hence with the phase of the solar cycle; iv) the occurrence frequency
of low-latitude aurora for 1780 - 1980 from the survey of Legrand and
Simon (Ann. Geophys. 5, 161, 1987). For all cases, RBB
exceeds the test terrestrial series by an amount that increases as
one goes back in time.
Title: Atmospheric ionization induced by precipitating electrons:
Comparison of CRAC:EPII model with a parametrization model
Authors: Artamonov, A. A.; Mishev, A. L.; Usoskin, I. G.
Bibcode: 2016JASTP.149..161A
Altcode: 2016arXiv160105910A
Results of a comparison of a new model CRAC:EPII (Cosmic Ray Atmospheric
Cascade: Electron Precipitation Induced Ionization) with a commonly used
parametric model of atmospheric ionization is presented. The CRAC:EPII
is based on a Monte Carlo simulation of precipitating electrons
propagation and interaction with matter in the Earth's atmosphere. It
explicitly considers energy deposit: ionization, pair production,
Compton scattering, generation of Bremsstrahlung high energy photons,
photo-ionization and annihilation of positrons, multiple scattering as
physical processes accordingly. Propagation of precipitating electrons
and their interactions with air is simulated with the GEANT4 simulation
tool PLANETOCOSMICS code using NRLMSISE-00 atmospheric model. Ionization
yields are computed and compared with a parametrization model for
different energies of incident precipitating energetic electrons, using
simulated fluxes of mono-energetic particles. A good agreement between
the two models is achieved in the mesosphere but the contribution of
Bremsstrahlung in the stratosphere, which is not accounted for in the
parametric models, is found significant. As an example, we calculated
profiles of the ion production rates in the middle and upper atmosphere
(below 100 km) on the basis of balloon-born measured spectra of
precipitating electrons for 30-October-2002 and 07-January-2004.
Title: A New Calibrated Sunspot Group Series Since 1749: Statistics
of Active Day Fractions
Authors: Usoskin, I. G.; Kovaltsov, G. A.; Lockwood, M.; Mursula,
K.; Owens, M.; Solanki, S. K.
Bibcode: 2016SoPh..291.2685U
Altcode: 2016SoPh..tmp....6U; 2015arXiv151206421U
Although sunspot-number series have existed since the mid-nineteenth
century, they are still the subject of intense debate, with the largest
uncertainty being related to the "calibration" of the visual acuity
of individual observers in the past. A daisy-chain regression method
is usually applied to inter-calibrate the observers, which may lead
to significant bias and error accumulation. Here we present a novel
method for calibrating the visual acuity of the key observers to the
reference data set of Royal Greenwich Observatory sunspot groups for the
period 1900 - 1976, using the statistics of the active-day fraction. For
each observer we independently evaluate their observational thresholds
[SS] defined such that the observer is assumed to miss all
of the groups with an area smaller than SS and report all
the groups larger than SS. Next, using a Monte-Carlo method,
we construct a correction matrix for each observer from the reference
data set. The correction matrices are significantly non-linear and
cannot be approximated by a linear regression or proportionality. We
emphasize that corrections based on a linear proportionality between
annually averaged data lead to serious biases and distortions of the
data. The correction matrices are applied to the original sunspot-group
records reported by the observers for each day, and finally the
composite corrected series is produced for the period since 1748. The
corrected series is provided as supplementary material in electronic
form and displays secular minima around 1800 (Dalton Minimum) and 1900
(Gleissberg Minimum), as well as the Modern Grand Maximum of activity in
the second half of the twentieth century. The uniqueness of the grand
maximum is confirmed for the last 250 years. We show that the adoption
of a linear relationship between the data of Wolf and Wolfer results
in grossly inflated group numbers in the eighteenth and nineteenth
centuries in some reconstructions.
Title: VizieR Online Data Catalog: Butterfly diagram wings (Leussu+,
2017)
Authors: Leussu, R.; Usoskin, I. G.; Senthamizh Pavai, V.; Diercke,
A.; Arlt, R.; Mursula, K.
Bibcode: 2016yCat..35990131L
Altcode:
fig1data.dat contains the separated wings in a butterfly diagram for
sunspot groups from three different origins: Sunspot observations
by S.H. Schwabe and G. Spoerer, and the RGO/SOON compilation. The
latitudes for sunspot groups from the Schwabe and Spoerer data
are given as size-weighted averages from sunspots belonging to each
group. Latitudes for the RGO compilation are given as they are stated
in the original data. The columns report the year, month, day, date
[yr], latitude [deg], cycle, hemisphere, and data set tag. Northern
hemisphere wings are tagged with "1" and southern hemisphere wings with
"2". The data set tag is "1" for Schwabe data, "2" for Spoerer data and
"3" for RGO data. (1 data file).
Title: Tests of Sunspot Number Sequences: 3. Effects of Regression
Procedures on the Calibration of Historic Sunspot Data
Authors: Lockwood, M.; Owens, M. J.; Barnard, L.; Usoskin, I. G.
Bibcode: 2016SoPh..291.2829L
Altcode: 2015arXiv151007809L; 2016SoPh..tmp...20L
We use sunspot-group observations from the Royal Greenwich Observatory
(RGO) to investigate the effects of intercalibrating data from observers
with different visual acuities. The tests are made by counting the
number of groups [RB] above a variable cut-off threshold
of observed total whole spot area (uncorrected for foreshortening)
to simulate what a lower-acuity observer would have seen. The
synthesised annual means of RB are then re-scaled to
the full observed RGO group number [RA] using a variety
of regression techniques. It is found that a very high correlation
between RA and RB (rAB>0.98 )
does not prevent large errors in the intercalibration (for example
sunspot-maximum values can be over 30 % too large even for such
levels of rAB). In generating the backbone sunspot number
[RBB], Svalgaard and Schatten (Solar Phys., 2016) force
regression fits to pass through the scatter-plot origin, which generates
unreliable fits (the residuals do not form a normal distribution) and
causes sunspot-cycle amplitudes to be exaggerated in the intercalibrated
data. It is demonstrated that the use of Quantile-Quantile ("Q-Q") plots
to test for a normal distribution is a useful indicator of erroneous
and misleading regression fits. Ordinary least-squares linear fits,
not forced to pass through the origin, are sometimes reliable (although
the optimum method used is shown to be different when matching peak
and average sunspot-group numbers). However, other fits are only
reliable if non-linear regression is used. From these results it is
entirely possible that the inflation of solar-cycle amplitudes in the
backbone group sunspot number as one goes back in time, relative to
related solar-terrestrial parameters, is entirely caused by the use
of inappropriate and non-robust regression techniques to calibrate
the sunspot data.
Title: Balloon measurements of the vertical ionization profile over
southern Israel and comparison to mid-latitude observations
Authors: Yaniv, Roy; Yair, Yoav; Price, Colin; Nicoll, Keri; Harrison,
Giles; Artamonov, Anton; Usoskin, Ilya
Bibcode: 2016JASTP.149...87Y
Altcode:
Airborne measurements using meteorological balloons were conducted
for the first time from southern Israel (geographic 30°35'N, 34°45'E
geomagnetic 27°6'N 112°23'E) for measuring the vertical ionization
profile during solar cycle 24. The results show the differences
(increase of 30%) in count rates as we proceed from solar maximum
toward solar minimum. The observed altitude of maximum ionization
(the Regener-Pfotzer maximum) was between 17-20 km, and it agrees
well with results from other simultaneous measurements conducted at
different latitudes (Reading, UK and Zaragoza-Barcelona, Spain). When
compared with predictions of an analytical model, we find a highly
significant correlation (R2=0.97) between our observations
and the computed ionization profiles. The difference in count rates can
be attributed to the height of the tropopause due to the model using
a US standard atmosphere that differs from the measured atmospheric
parameters above Israel.
Title: Properties of sunspot cycles and hemispheric wings since the
19th century
Authors: Leussu, Raisa; Usoskin, Ilya G.; Arlt, Rainer; Mursula, Kalevi
Bibcode: 2016A&A...592A.160L
Altcode:
Aims: The latitudinal evolution of sunspot emergence over
the course of the solar cycle, the so-called butterfly diagram, is a
fundamental property of the solar dynamo. Here we present a study of
the butterfly diagram of sunspot group occurrence for cycles 7-10 and
11-23 using data from a recently digitized sunspot drawings by Samuel
Heinrich Schwabe in 1825-1867, and from RGO/USAF/NOAA(SOON) compilation
of sunspot groups in 1874-2015.
Methods: We developed a new,
robust method of hemispheric wing separation based on an analysis of
long gaps in sunspot group occurrence in different latitude bands. The
method makes it possible to ascribe each sunspot group to a certain
wing (solar cycle and hemisphere), and separate the old and new cycle
during their overlap. This allows for an improved study of solar
cycles compared to the common way of separating the cycles.
Results: We separated each hemispheric wing of the butterfly diagram
and analysed them with respect to the number of groups appearing in
each wing, their lengths, hemispheric differences, and overlaps.
Conclusions: The overlaps of successive wings were found to be
systematically longer in the northern hemisphere for cycles 7-10,
but in the southern hemisphere for cycles 16-22. The occurrence of
sunspot groups depicts a systematic long-term variation between the
two hemispheres. During Schwabe time, the hemispheric asymmetry was
north-dominated during cycle 9 and south-dominated during cycle 10.
Title: Corrigendum to 'A review of Holocene solar-linked climatic
variation on centennial to millennial timescales: Physical processes,
interpretative frameworks and a new multiple cross-wavelet transform
algorithm' Earth Sci. Rev. 134 [1-15]
Authors: Soon, Willie; Velasco Herrera, Victor M.; Selvaraj, Kandasamy;
Traversi, Rita; Usoskin, Ilya; Arthur Chen, Chen-Tung; Lou, Jiann-Yuh;
Kao, Shuh-Ji; Carter, Robert M.; Pipin, Valery; Severi, Mirko;
Becagli, Silvia
Bibcode: 2016ESRv..159..462S
Altcode:
In the article "A review of Holocene solar-linked climatic variation on
centennial to millennial timescales: Physical processes, interpretative
frameworks and a new multiple cross-wavelet transform algorithm",
published in Earth-Science Reviews 134 (2014) 1, it was omitted to
state that at the time this article was submitted the corresponding
author Dr. Soon received funding from the Southern Company Services and
Donors Trust. We have no indication that this funding has influenced
the results presented in the article.
Title: Production of cosmogenic isotopes 7Be,
10Be, 14C, 22Na, and 36Cl
in the atmosphere: Altitudinal profiles of yield functions
Authors: Poluianov, S. V.; Kovaltsov, G. A.; Mishev, A. L.; Usoskin,
I. G.
Bibcode: 2016JGRD..121.8125P
Altcode: 2016arXiv160605899P
New consistent and precise computations of the production of
five cosmogenic radioisotopes, 7Be, 10Be,
14C, 22Na, and 36Cl, in the Earth's
atmosphere by cosmic rays are presented in the form of tabulated yield
functions. For the first time, a detailed set of the altitude profiles
of the production functions is provided which makes it possible to apply
the results directly as input for atmospheric transport models. Good
agreement with most of the earlier published works for columnar and
global isotopic production rates is shown. Altitude profiles of the
production are important, in particular for such tasks as studies of
strong solar particle events in the past, precise reconstructions of
solar activity on long-term scale, tracing air mass dynamics using
cosmogenic radioisotopes, etc. As an example, computations of the
10Be deposition flux in the polar region are shown for the
last decades and also for a period around 780 A.D. and confronted with
the actual measurements in Greenland and Antarctic ice cores.
Title: Solar total and spectral irradiance reconstruction over last
9000 years
Authors: Wu, Chi-Ju; Usoskin, Ilya; Krivova, Natalie; Solanki, Sami K.
Bibcode: 2016cosp...41E2072W
Altcode:
Although the mechanisms of solar influence on Earth climate system
are not yet fully understood, solar total and spectral irradiance are
considered to be among the main determinants. Solar total irradiance
is the total flux of solar radiative energy entering Earth's climate
system, whereas the spectral irradiance describes this energy is
distributed over the spectrum. Solar irradiance in the UV band is of
special importance since it governs chemical processes in the middle and
upper atmosphere. On timescales of the 11-year solar cycle and shorter,
solar irradiance is measured by space-based instruments while models
are needed to reconstruct solar irradiance on longer timescale. The
SATIRE-M model (Spectral And Total Irradiance Reconstruction over
millennia) is employed in this study to reconstruct solar irradiance
from decadal radionuclide isotope data such as 14C and 10Be stored in
tree rings and ice cores, respectively. A reconstruction over the last
9000 years will be presented.
Title: Near-Earth heliospheric magnetic field intensity since 1750:
2. Cosmogenic radionuclide reconstructions
Authors: Owens, M. J.; Cliver, E.; McCracken, K. G.; Beer, J.; Barnard,
L.; Lockwood, M.; Rouillard, A.; Passos, D.; Riley, P.; Usoskin, I.;
Wang, Y. -M.
Bibcode: 2016JGRA..121.6064O
Altcode:
This is Part 2 of a study of the near-Earth heliospheric magnetic field
strength, B, since 1750. Part 1 produced composite estimates of B from
geomagnetic and sunspot data over the period 1750-2013. Sunspot-based
reconstructions can be extended back to 1610, but the paleocosmic ray
(PCR) record is the only data set capable of providing a record of
solar activity on millennial timescales. The process for converting
10Be concentrations measured in ice cores to B is more
complex than with geomagnetic and sunspot data, and the uncertainties
in B derived from cosmogenic nuclides (~20% for any individual year)
are much larger. Within this level of uncertainty, we find reasonable
overall agreement between PCR-based B and the geomagnetic- and sunspot
number-based series. This agreement was enhanced by excising low values
in PCR-based B attributed to high-energy solar proton events. Other
discordant intervals, with as yet unspecified causes remain included in
our analysis. Comparison of 3 year averages centered on sunspot minimum
yields reasonable agreement between the three estimates, providing a
means to investigate the long-term changes in the heliospheric magnetic
field into the past even without a means to remove solar proton events
from the records.
Title: Near-Earth heliospheric magnetic field intensity since 1750:
1. Sunspot and geomagnetic reconstructions
Authors: Owens, M. J.; Cliver, E.; McCracken, K. G.; Beer, J.; Barnard,
L.; Lockwood, M.; Rouillard, A.; Passos, D.; Riley, P.; Usoskin, I.;
Wang, Y. -M.
Bibcode: 2016JGRA..121.6048O
Altcode:
We present two separate time series of the near-Earth heliospheric
magnetic field strength (B) based on geomagnetic data and sunspot number
(SSN). The geomagnetic-based B series from 1845 to 2013 is a weighted
composite of two series that employ the interdiurnal variability index;
this series is highly correlated with in situ spacecraft measurements
of B (correlation coefficient, r = 0.94; mean square error, MSE =
0.16 nT2). The SSN-based estimate of B, from 1750 to 2013,
is a weighted composite of eight time series derived from two separate
reconstruction methods applied to four different SSN time series,
allowing determination of the uncertainty from both the underlying
sunspot records and the B reconstruction methods. The SSN-based
composite is highly correlated with direct spacecraft measurements of B
and with the composite geomagnetic B time series from 1845 to 2013 (r =
0.91; MSE = 0.24 nT2), demonstrating that B can accurately
reconstructed by both geomagnetic and sunspot-based methods. The
composite sunspot and geomagnetic B time series, with uncertainties,
are provided as supporting information.
Title: Application of the new neutron monitor yield function computed
for different altitudes to an analysis of GLEs
Authors: Mishev, Alexander; Usoskin, Ilya
Bibcode: 2016cosp...41E1310M
Altcode:
A precise analysis of SEP (solar energetic particle) spectral and
angular characteristics using neutron monitor (NM) data requires
realistic modeling of propagation of those particles in the Earth's
magnetosphere and atmosphere. On the basis of the method including a
sequence of consecutive steps, namely a detailed computation of the
SEP assymptotic cones of acceptance, and application of a neutron
monitor yield function and convenient optimization procedure, we
derived the rigidity spectra and anisotropy characteristics of several
major GLEs. Here we present several major GLEs of the solar cycle 23:
the Bastille day event on 14 July 2000 (GLE 59), GLE 69 on 20 January
2005, and GLE 70 on 13 December 2006. The SEP spectra and pitch angle
distributions were computed in their dynamical development. For the
computation we use the newly computed yield function of the standard
6NM64 neutron monitor for primary proton and alpha CR nuclei. In
addition, we present new computations of NM yield function for the
altitudes of 3000 m and 5000 m above the sea level The computations
were carried out with Planetocosmics and CORSIKA codes as standardized
Monte-Carlo tools for atmospheric cascade simulations. The flux of
secondary neutrons and protons was computed using the Planetocosmics
code appliyng a realistic curved atmospheric. Updated information
concerning the NM registration efficiency for secondary neutrons
and protons was used. The derived results for spectral and angular
characteristics using the newly computed NM yield function at several
altitudes are compared with the previously obtained ones using the
double attenuation method.
Title: Modeling impact ionization of precipitating particles in the
upper and middle atmosphere
Authors: Mishev, Alexander; Usoskin, Ilya; Artamonov, Anton
Bibcode: 2016cosp...41E1309M
Altcode:
An extension of the cosmic ray ionization model CRAC:EPII (Cosmic
Ray Atmospheric Cascade: Electron Precipitation Induced Ionization)
is presented. It aims computation of electron impact ionization in
the atmosphere. The CRAC:EPII is based on Monte Carlo simulations of
electron propagation and interaction with matter, namely atmospheric
molecules. It explicitly considers various physical process, namely pair
production, Compton scattering, generation of Bremsstrahlung photons,
photo-ionization, annihilation of positrons, multiple scattering
as well as energy deposit and accordingly ionization. Propagation
of precipitating electrons and their interactions with atmospheric
molecules is modelled with the the PLANETOCOSMICS code. The atmospheric
model NRLMSISE 2000 is used. The yield functions for computation of
electron impact ionization are presented. A quantitative comparison
with a parameterization driven model of the atmospheric ionization
induced by precipitating electronsis is carried out. A good agreement
is demonstrated. Several example electron spectra based on balloon-born
measurements are used as input in the model in order to compute ion
production in the upper and middle atmosphere. An updated ionization
yield function by primary cosmic ray protons in the upper/middle
atmosphere is also presented. Several examples of ion production in the
upper and middle atmosphere due to precipitating particles are shown.
Title: An Assessment of Sunspot Number Data Composites over 1845-2014
Authors: Lockwood, M.; Owens, M. J.; Barnard, L.; Usoskin, I. G.
Bibcode: 2016ApJ...824...54L
Altcode: 2016arXiv160404538L
New sunspot data composites, some of which are radically different in
the character of their long-term variation, are evaluated over the
interval 1845-2014. The method commonly used to calibrate historic
sunspot data, relative to modern-day data, is “daisy-chaining,”
whereby calibration is passed from one data subset to the neighboring
one, usually using regressions of the data subsets for the intervals
of their overlap. Recent studies have illustrated serious pitfalls in
these regressions, and the resulting errors can be compounded by their
repeated use as the data sequence is extended back in time. Hence, the
recent composite data series by Usoskin et al., R UEA, is a
very important advance because it avoids regressions, daisy-chaining,
and other common, but invalid, assumptions: this is achieved by
comparing the statistics of “active-day” fractions to those
for a single reference data set. We study six sunspot data series,
including R UEA and the new “backbone” data series
(R BB, recently generated by Svalgaard & Schatten by
employing both regression and daisy-chaining). We show that all six
can be used with a continuity model to reproduce the main features
of the open solar flux variation for 1845-2014, as reconstructed from
geomagnetic activity data. However, some differences can be identified
that are consistent with tests using a basket of other proxies for
solar magnetic fields. Using data from a variety of sunspot observers,
we illustrate problems with the method employed in generating R
BB that cause it to increasingly overestimate sunspot
numbers going back in time, and we recommend using R UEA
because it employs more robust procedures that avoid such problems.
Title: Erratum: Erratum to: Analysis of the ground level enhancements
on 14 July 2000 and on 13 December 2006 using neutron monitor data
Authors: Mishev, A.; Usoskin, I.
Bibcode: 2016SoPh..291.1579M
Altcode: 2016SoPh..tmp..106M
No abstract at ADS
Title: Semi-empirical Long-term Reconstruction of the Heliospheric
Parameters: Validation by Cosmogenic Radionuclide Records
Authors: Asvestari, E.; Usoskin, I. G.; Cameron, R. H.; Krivova, N. A.
Bibcode: 2016ASPC..504..269A
Altcode:
We have developed a semi-empirical model that describes the heliospheric
modulation of galactic cosmic rays considering different heliospheric
parameters. This model is an improvement of a previous model. The
parameters of the model are fitted using the observations and
reconstructions of the heliospheric parameters for the period 1976 -
2013, which includes the latest very weak solar minimum. The modulation
potential is computed since 1610 using different reconstructions of the
open solar magnetic flux and it is then used to compute the production
and distribution of cosmogenic isotope 14C, which was
subsequently compared with terrestrial archives in tree rings. It is
shown that the group sunspot number series by Svalgaard & Schatten
(2015) is inconsistent with the data, while other series agree well.
Title: Extreme solar particle events: The worst case scenario
Authors: Usoskin, Ilya; Kovaltsov, Gennady
Bibcode: 2016EGUGA..18.3898U
Altcode:
Sporadic eruptive energetic events on the Sun may occur during
periods of high solar activity. Sometimes such events can be strong
or even extreme posing serious hazards for the modern technology
and communication dependent society. It is important to asses the
worst case scenario for an extreme solar particle event and what the
probability of its occurrence. The era of direct scientific exploration
of the Sun is short - from few decades to a century, and yet several
strong harmful events took place during that time. Can we expect even
greater events? How often? What shall we prepare for? In order to answer
these questions, one has to rely upon indirect methods by analyzing
natural proxy archives. Here we present an overview of the history of
extreme solar events in the past, from hundreds to millions of year,
based on an analysis of cosmogenic isotopes in terrestrial archives
(polar ice cores and tree rings) and in lunar rocks.
Title: Analysis of the Ground-Level Enhancements on 14 July 2000
and 13 December 2006 Using Neutron Monitor Data
Authors: Mishev, A.; Usoskin, I.
Bibcode: 2016SoPh..291.1225M
Altcode: 2016SoPh..tmp...46M; 2016arXiv160308918M
On the basis of neutron monitor data, we estimate the energy spectrum,
anisotropy axis direction, and pitch-angle distribution of solar
energetic particles during two major ground-level enhancements (GLE
59 on 14 July 2000 and GLE 70 on 13 December 2006). For the analysis
we used a newly computed neutron monitor yield function. The method
consists of several consecutive steps: definition of the asymptotic
viewing cones of neutron monitor stations considered for the data
analysis by computing the cosmic ray particle propagation in a
model magnetosphere with the MAGNETOCOSMICS code, computing the
neutron monitor model responses, and deriving the solar energetic
particle characteristics on the basis of inverse problem solution. The
pitch-angle distribution and rigidity spectrum of high-energy protons
are obtained as a function of time in the course of ground-level
enhancements. A comparison with previously reported results is performed
and reasonable agreement is achieved. A discussion of the obtained
results is included.
Title: Solar activity during the Holocene: the Hallstatt cycle and
its consequence for grand minima and maxima
Authors: Usoskin, I. G.; Gallet, Y.; Lopes, F.; Kovaltsov, G. A.;
Hulot, G.
Bibcode: 2016A&A...587A.150U
Altcode: 2016arXiv160202483U
Aims: Cosmogenic isotopes provide the only quantitative proxy
for analyzing the long-term solar variability over a centennial
timescale. While essential progress has been achieved in both
measurements and modeling of the cosmogenic proxy, uncertainties
still remain in the determination of the geomagnetic dipole
moment evolution. Here we aim at improving the reconstruction of
solar activity over the past nine millennia using a multi-proxy
approach.
Methods: We used records of the 14C and
10Be cosmogenic isotopes, current numerical models of the
isotope production and transport in Earth's atmosphere, and available
geomagnetic field reconstructions, including a new reconstruction
relying on an updated archeo- and paleointensity database. The
obtained series were analyzed using the singular spectrum analysis
(SSA) method to study the millennial-scale trends.
Results:
A new reconstruction of the geomagnetic dipole field moment,
referred to as GMAG.9k, is built for the last nine millennia. New
reconstructions of solar activity covering the last nine millennia,
quantified in terms of sunspot numbers, are presented and analyzed. A
conservative list of grand minima and maxima is also provided.
Conclusions: The primary components of the reconstructed solar activity,
as determined using the SSA method, are different for the series that
are based on 14C and 10Be. This shows that
these primary components can only be ascribed to long-term changes
in the terrestrial system and not to the Sun. These components have
therefore been removed from the reconstructed series. In contrast,
the secondary SSA components of the reconstructed solar activity are
found to be dominated by a common ≈2400-year quasi-periodicity,
the so-called Hallstatt cycle, in both the 14C and
10Be based series. This Hallstatt cycle thus appears to be
related to solar activity. Finally, we show that the grand minima and
maxima occurred intermittently over the studied period, with clustering
near lows and highs of the Hallstatt cycle, respectively. Tables
C.1 and C.2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/587/A150
Title: An empirical model of heliospheric cosmic ray modulation on
long-term time scale
Authors: Asvestari, Eleanna; Usoskin, Ilya G.
Bibcode: 2016JSWSC...6A..15A
Altcode:
Galactic Cosmic Rays (GCRs) entering the heliosphere are subject to
modulation processes due to variable solar magnetic activity. Finding
a relationship between cosmic-ray variations and the heliospheric
parameters is important for reconstruction of solar activity in
the past. Here, we develop a semi-empirical model describing
the heliospheric modulation of GCRs in terms of heliospheric
parameters such as the open solar magnetic flux, the tilt angle of
the heliospheric current sheet and the polarity of the large scale
solar magnetic field. Our model is fitted using annual data obtained
for the period 1976-2013, which includes the very weak solar minimum
during 2008-2010. The model shows a good agreement with the data,
and therefore, can be used for reconstructions of the modulation
potential at different levels of solar activity. The model's validity
is also tested using the cosmogenic radionuclides 14C
and 10Be stored in terrestrial archives. The tilt angle
used to fit the parameters in our semi-empirical modulation model is
reconstructed by a mathematical model described here.
Title: Model CRAC:EPII for atmospheric ionization due to precipitating
electrons: Yield function and applications
Authors: Artamonov, A. A.; Mishev, A. L.; Usoskin, I. G.
Bibcode: 2016JGRA..121.1736A
Altcode:
A new model of the family of CRAC models, CRAC:EPII (Cosmic Ray
Atmospheric Cascade: Electron Precipitation Induced Ionization),
is presented. The model calculates atmospheric ionization induced
by precipitating electrons and uses the formalism of ionization
yield functions. The CRAC:EPII model is based on a full Monte Carlo
simulation of electron propagation and interaction with the air
molecules. It explicitly considers various physical processes, namely,
pair production, Compton scattering, generation of bremsstrahlung
high-energy photons, photoionization, annihilation of positrons,
and multiple scattering. The simulations were performed using GEANT 4
simulation tool PLANETOCOSMICS with NRLMSISE 00 atmospheric model. The
CRAC:EPII model is applicable to the entire atmosphere. The results from
the simulations are given as look-up table representing the ionization
yield function. The table allows one to compute ionization due to
precipitating electrons for a given altitude and location considering
a given electron spectrum. Application of the model for computation
of ion production during electron precipitation events using spectra
from balloon-borne measurements is presented.
Title: VizieR Online Data Catalog: Solar activity during the Holocene
(Usoskin+, 2016)
Authors: Usoskin, I. G.; Gallet, Y.; Lopes, F.; Kovaltsov, G. A.;
Hulot, G.
Bibcode: 2016yCat..35870150U
Altcode:
tables1.dat contains axial dipole evolution between 1500 BC and 1900
AD as constrained by Virtual Axial Dipole Moments (VADM) averaged over
sliding windows of 200 years shifted every 10 years. tables2.dat
contains axial dipole evolution between 6750 BC and 1500 BC as
constrained by Virtual Axial Dipole Moments (VADM) averaged over
sliding windows of 500 years shifted every 10 years. Details on
the computations are provided in Appendix A. The columns report
the epoch [yr], the mean VADM [Gmean] (in units of 1022
Am2), the standard deviation [SD] and the maximum [Gmax]
and minimum [Gmin] values defining the envelope of possible VADM
results. (2 data files).
Title: Neutron monitor yield function for solar neutrons: A new
computation
Authors: Artamonov, A. A.; Kovaltsov, G. A.; Mishev, A. L.; Usoskin,
I. G.
Bibcode: 2016JGRA..121..117A
Altcode:
A new yield function of a standard neutron monitor 6NM64 for
solar neutrons is presented and tabulated in the attached lookup
tables. It corresponds to a wide range of altitudes of the neutron
monitor locations and angles of incidence for neutrons entering the
Earth's atmosphere. The computations were made by Monte Carlo using
the GEANT4-based PLANETOCOSMICS tool. The yield function was validated
against the measured data for solar neutron events of 3 June 1982 and
24 May 1990, and good agreement was found within a wide range of the
altitudes of the neutron monitor location and angles of incidence of
solar neutron arrival. The sensitivity of the world neutron monitor
network for registration of solar neutron events was reassessed. The
neutron monitor network is shown to be, in addition to other methods,
a sensitive tool for monitoring of high-energy solar-flare neutrons
with ≈95% probability to detect statistically significantly (>5σ)
a solar neutron event similar to that of 3 June 1982.
Title: A two-wave dynamo model by Zharkova et al. (2015) disagrees
with data on long-term solar variability
Authors: Usoskin, I.; Kovaltsov, G.
Bibcode: 2015arXiv151205516U
Altcode:
A two-wave dynamo model was recently proposed by Zharkova et al. (2015,
Zh15 henceforth), which aims at long-term predictions of solar activity
for millennia ahead and backwards. Here we confront the backward
model predictions for the last 800 years with known variability of
solar activity, using both direct sunspot observations since 1610 and
reconstructions based on cosmogenic radionuclide data. We show that
the Zh15 model fails to reproduce the well-established features of
the solar activity evolution during the last millennium. This means
that the predictive part for the future is not reliable either.
Title: Mini Neutron Monitors at Concordia Research Station, Central
Antarctica
Authors: Poluianov, Stepan; Usoskin, Ilya; Mishev, Alexander; Moraal,
Harm; Kruger, Helena; Casasanta, Giampietro; Traversi, Rita; Udisti,
Roberto
Bibcode: 2015JASS...32..281P
Altcode:
Two mini neutron monitors are installed at Concordia research
station (Dome C, Central Antarctica, 75° 06' S, 123° 23' E,
3,233 m.a.s.l.). The site has unique properties ideal for cosmic ray
measurements, especially for the detection of solar energetic particles:
very low cutoff rigidity < 0.01 GV, high elevation and poleward
asymptotic acceptance cones pointing to geographical latitudes >
75° S. The instruments consist of a standard neutron monitor and a
"bare" (lead-free) neutron monitor. The instrument operation started in
mid-January 2015. The barometric correction coefficients were computed
for the period from 1 February to 31 July 2015. Several interesting
events, including two notable Forbush decreases on 17 March 2015
and 22 June 2015, and a solar particle event of 29 October 2015
were registered. The data sets are available at cosmicrays.oulu.fi
and nmdb.eu.
Title: The carbon-14 spike in the 8th century was not caused by a
cometary impact on Earth
Authors: Usoskin, Ilya G.; Kovaltsov, Gennady A.
Bibcode: 2015Icar..260..475U
Altcode: 2014arXiv1401.5945U
A mysterious increase of radiocarbon 14 C ca. 775 AD in the
Earth's atmosphere has been recently found by Miyake et al. (Miyake,
F., Nagaya, K., Masuda, K., Nakamura, T. [2012]. Nature, 486,
240). A possible source of this event has been discussed widely,
the most likely being an extreme solar energetic particle event. A
new exotic hypothesis has been presented recently by Liu et al. (Liu,
Y. [2014]. Sci. Rep., 4, 3728) who proposed that the event was caused
by a cometary impact on Earth bringing additional 14 C to
the atmosphere. Here we calculated a realistic mass and size of such
a comet to show that it would have been huge (≈100 km across and
1017-1020 g of mass) and would have produced a
disastrous geological/biological impact on Earth. The absence of an
evidence for such a dramatic event makes this hypothesis invalid.
Title: Energetic Particle Influence on the Earth's Atmosphere
Authors: Mironova, Irina A.; Aplin, Karen L.; Arnold, Frank;
Bazilevskaya, Galina A.; Harrison, R. Giles; Krivolutsky, Alexei A.;
Nicoll, Keri A.; Rozanov, Eugene V.; Turunen, Esa; Usoskin, Ilya G.
Bibcode: 2015SSRv..194....1M
Altcode: 2015SSRv..tmp...78M
This manuscript gives an up-to-date and comprehensive overview
of the effects of energetic particle precipitation (EPP) onto the
whole atmosphere, from the lower thermosphere/mesosphere through the
stratosphere and troposphere, to the surface. The paper summarizes the
different sources and energies of particles, principally galactic cosmic
rays (GCRs), solar energetic particles (SEPs) and energetic electron
precipitation (EEP). All the proposed mechanisms by which EPP can
affect the atmosphere are discussed, including chemical changes in the
upper atmosphere and lower thermosphere, chemistry-dynamics feedbacks,
the global electric circuit and cloud formation. The role of energetic
particles in Earth's atmosphere is a multi-disciplinary problem that
requires expertise from a range of scientific backgrounds. To assist
with this synergy, summary tables are provided, which are intended to
evaluate the level of current knowledge of the effects of energetic
particles on processes in the entire atmosphere.
Title: The Maunder minimum (1645-1715) was indeed a grand minimum:
A reassessment of multiple datasets
Authors: Usoskin, Ilya G.; Arlt, Rainer; Asvestari, Eleanna; Hawkins,
Ed; Käpylä, Maarit; Kovaltsov, Gennady A.; Krivova, Natalie;
Lockwood, Michael; Mursula, Kalevi; O'Reilly, Jezebel; Owens, Matthew;
Scott, Chris J.; Sokoloff, Dmitry D.; Solanki, Sami K.; Soon, Willie;
Vaquero, José M.
Bibcode: 2015A&A...581A..95U
Altcode: 2015arXiv150705191U
Aims: Although the time of the Maunder minimum (1645-1715) is
widely known as a period of extremely low solar activity, it is still
being debated whether solar activity during that period might have
been moderate or even higher than the current solar cycle #24. We have
revisited all existing evidence and datasets, both direct and indirect,
to assess the level of solar activity during the Maunder minimum.
Methods: We discuss the East Asian naked-eye sunspot observations, the
telescopic solar observations, the fraction of sunspot active days,
the latitudinal extent of sunspot positions, auroral sightings at
high latitudes, cosmogenic radionuclide data as well as solar eclipse
observations for that period. We also consider peculiar features of
the Sun (very strong hemispheric asymmetry of the sunspot location,
unusual differential rotation and the lack of the K-corona) that imply
a special mode of solar activity during the Maunder minimum.
Results: The level of solar activity during the Maunder minimum is
reassessed on the basis of all available datasets.
Conclusions:
We conclude that solar activity was indeed at an exceptionally low
level during the Maunder minimum. Although the exact level is still
unclear, it was definitely lower than during the Dalton minimum of
around 1800 and significantly below that of the current solar cycle
#24. Claims of a moderate-to-high level of solar activity during the
Maunder minimum are rejected with a high confidence level.
Title: Comparative Morphology of Solar Relativistic Particle Events
Authors: Kocharov, Leon; Klassen, Andreas; Valtonen, Eino; Usoskin,
Ilya; Ryan, James M.
Bibcode: 2015ApJ...811L...9K
Altcode:
Time profiles of the 0.25-10 MeV electrons and the ∼(0.1-1) GeV
nucleon-1 protons and helium associated with two solar
coronal mass ejections (CMEs) are analyzed with a newly formulated
method based on modeling of the particle transport in the interplanetary
medium. With the modeling, we fit the observed angular distribution
of solar particles and infer, for a particular particle instrument and
magnetic field orientation, the time delay of the particle registration
at 1 AU in respect to the solar source. Then, after the time offset
removal, intensity re-normalization and background equalization, the
time-intensity profiles of high-energy protons, helium and electrons in
different energy channels are superposed and compared. The comparison
reveals episodes of remarkable coincidence of different profiles, as
well as episodes of essentially different behavior. It implies at least
three sources of solar high-energy particles operating in a single
event. The first, short-duration source emits electrons next to the
flare's impulsive phase and CME liftoff. The second source gradually
rises and continues for more than an hour, emitting electrons and
lower energy protons, which is consistent with shock acceleration on
open magnetic field lines extending to solar wind. An another, third
source is the main source of relativistic ions in space. It is retarded
in respect to the flare's impulsive phase and may be associated with
a structure encountered by the shock within a few solar radii from
the Sun.
Title: Can we properly model the neutron monitor count rate?
Authors: Gil, Agnieszka; Usoskin, Ilya G.; Kovaltsov, Gennady A.;
Mishev, Alexander L.; Corti, Claudio; Bindi, Veronica
Bibcode: 2015JGRA..120.7172G
Altcode:
Neutron monitors provide continuous measurements of secondary nucleonic
particles produced in the atmosphere by the primary cosmic rays and form
the main tool to study the heliospheric modulation of cosmic rays. In
order to study cosmic rays using the world network of neutron monitor
and needs to be able to model the neutron monitor count rate. Earlier
it was difficult because of the poorly known yield function, which has
been essentially revisited recently. We have presented a verification
of the new yield function of the standard neutron monitor (NM) using
a recently released data on the direct in situ measurements of the
galactic cosmic rays energy spectrum during 2006-2009 (the period of
the record high cosmic ray flux) by Payload for Antimatter Matter
Exploration and Light-nuclei Astrophysics spaceborne spectrometer,
and on NM latitude surveys performed during the period of 1994-2007,
including periods of high solar activity. We found a very good agreement
between the measured count rates of sea level NMs and the modeled
ones in very different conditions: from low to high solar activity and
from polar to tropical regions. This implies that the count rate of a
sea level neutron monitor can be properly modeled in all conditions,
using the new yield function.
Title: The Maunder minimum: A reassessment from multiple dataset
Authors: Usoskin, Ilya; Arlt, Rainer; Asvestari, Eleanna; Kovaltsov,
Gennady; Krivova, Natalie; Lockwood, Michael; Käpylä, Maarit; Owens,
Matthew; Sokoloff, Dmitry D.; Solanki, Sami; Soon, Willie; Vaquero,
Jose; Scott, Chris
Bibcode: 2015IAUGA..2253036U
Altcode:
The Maunder minimum (MM) in 1645-1715 was a period of the lowest ever
known solar activity recorded via sunspot numbers since 1610. Since
it is the only Grand minimum of solar activity directly observed,
it forms a benchmark for the solar variability studies. Therefore,
it is crucially important to assess the level and other features
of temporal and spatial solar magnetic variability during that
time. However, because of uncertainties related mostly to ambiguity
of some historical sunspot observation records, the exact level of
solar activity during the MM is somewhat unclear, leaving room for
continuous discussions and speculations. Many of these issues have been
addressed by Jack Eddy in his cornerstone papers of 1976 and 1983,
but since then numerous new pieces of evidence and datasets have
appeared, making it possible to verify the paradigm of the Maunder
minimum with far greater certainty than before.Here we provide a full
reassessment of the Maunder minimum using all the available datasets:
augmented sunspot counts and drawings; revisited historical archives;
both well-known and newly revealed records of auroral observations;
cosmic ray variability via cosmogenic isotope records of 14C
in tree trunks, 10Be in ice cores and 44Ti in
fallen meteorites. We show that, while the exact level of the activity
is not easy to determine, the Sun indeed exhibited exceptionally low
magnetic activity during the MM, in comparison to other periods of
moderate or decreased activity, such as the Dalton minimum (ca. 1800),
the Gleissberg minimum (ca. 1900) and the present weak solar cycle #
24. We show that a scenario of moderate or strong activity during the
MM contradicts all the available datasets.Thus, we confirm, using
all the presently available datasets of different nature, that the
period of the Maunder minimum in 1645-1715 was indeed a Grand minimum,
with very low solar surface magnetic activity, low intensity of the
interplanetary magnetic field, as well as lower frequency and higher
geographical latitude of auroral occurrence. Meanwhile some indications
of the continuation, but at a very low level, of the 11-year solar
cycle can be found in the data.
Title: A mini neutron monitor in Central Antarctica (Dome Concordia)
Authors: Usoskin, I.; Poluianov, S.; Moraal, H.; Krüger, H.;
Casasanta, G.; Traversi, R.; Udisty, R.
Bibcode: 2015ICRC...34..217U
Altcode: 2015PoS...236..217U
No abstract at ADS
Title: Has the Earth been exposed to numerous supernovae within the
last 300 kyr?
Authors: Melott, Adrian L.; Usoskin, Ilya G.; Kovaltsov, Gennady A.;
Laird, Claude M.
Bibcode: 2015IJAsB..14..375M
Altcode: 2014arXiv1406.5141M
Firestone (2014) asserted evidence for numerous (23) nearby (d < 300
pc) supernovae (SNe) within the Middle and Late Pleistocene. If true,
this would have strong implications for the irradiation of the Earth;
at this rate, the mass extinction level events due to SNe would be
more frequent than 100 Myr. However, there are numerous errors in the
application of past research. The paper overestimates likely nitrate
and 14C production from moderately nearby SNe by about four
orders of magnitude. Moreover, the results are based on wrongly selected
(obsolete) nitrate and 14C datasets. The use of correct and
up-to-date datasets does not confirm the claimed results. The claims
in the paper are invalid.
Title: A New neutron monitor yield function computed for different
altitudes: Application for a GLE analysis
Authors: Mishev, A.; Usoskin, I.; Kovaltsov, G.
Bibcode: 2015ICRC...34..159M
Altcode: 2015PoS...236..159M
No abstract at ADS
Title: Database of Ground Level Enhancements (GLE) of High Energy
Solar Proton Events
Authors: Usoskin, I.; Ibragimov, A.; Shea, M. A.; Smart, D. F.
Bibcode: 2015ICRC...34...54U
Altcode: 2015PoS...236...54U
No abstract at ADS
Title: Effective dose calculation at flight altitudes with the newly
computed yield function
Authors: Mishev, A.; Usoskin, I.
Bibcode: 2015ICRC...34..158M
Altcode: 2015PoS...236..158M
No abstract at ADS
Title: Use of cosmogenic radionuclides 14C and 10Be to verify
empirically reconstructed cosmic ray modulation since 1616
Authors: Asvestari, E.; Usoskin, I.; Kovaltsov, G.
Bibcode: 2015ICRC...34...53A
Altcode: 2015PoS...236...53A
No abstract at ADS
Title: Assessment of F200 fluence for major solar energetic particle
events on the multi-millennial time scale
Authors: Usoskin, I.; Kovaltsov, G.; Cliver, E.; Dietrich, W. F.;
Tylka, A.
Bibcode: 2015ICRC...34...18U
Altcode: 2015PoS...236...18U
No abstract at ADS
Title: Flux of solar energetic particles in the distant past: Data
from lunar rocks
Authors: Poluianov, S.; Artamonov, A.; Kovaltsov, G.; Usoskin, I.
Bibcode: 2015ICRC...34...51P
Altcode: 2015PoS...236...51P
No abstract at ADS
Title: Resolving multiple sources of solar relativistic particles
Authors: Kocharov, L.; Klassen, A.; Usoskin, I.; Valtonen, E.
Bibcode: 2015ICRC...34...57K
Altcode: 2015PoS...236...57K
No abstract at ADS
Title: Sensitivity of the world-wide neutron monitor network to
solar neutrons: A revised approach
Authors: Artamonov, A.; Kovaltsov, G.; Mishev, A. Alexander;
Usoskin, I.
Bibcode: 2015ICRC...34..163A
Altcode: 2015PoS...236..163A
No abstract at ADS
Title: Force-field parameterization of the galactic cosmic ray
spectrum: Validation for Forbush decreases
Authors: Usoskin, I. G.; Kovaltsov, G. A.; Adriani, O.; Barbarino,
G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov,
E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.;
Campana, D.; Carbone, R.; Carlson, P.; Casolino, M.; Castellini, G.;
De Donato, C.; De Santis, C.; De Simone, N.; Di Felice, V.; Formato,
V.; Galper, A. M.; Karelin, A. V.; Koldashov, S. V.; Koldobskiy, S.;
Krutkov, S. Y.; Kvashnin, A. N.; Leonov, A.; Malakhov, V.; Marcelli,
L.; Martucci, M.; Mayorov, A. G.; Menn, W.; Mergé, M.; Mikhailov,
V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria,
G.; Palma, F.; Panico, B.; Papini, P.; Pearce, M.; Picozza, P.;
Pizzolotto, C.; Ricci, M.; Ricciarini, S. B.; Rossetto, L.; Sarkar,
R.; Scotti, V.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov,
Y. I.; Vacchi, A.; Vannuccini, E.; Vasilyev, G. I.; Voronov, S. A.;
Yurkin, Y. T.; Zampa, G.; Zampa, N.; Zverev, V. G.
Bibcode: 2015AdSpR..55.2940U
Altcode:
A useful parametrization of the energy spectrum of galactic cosmic rays
(GCR) near Earth is offered by the so-called force-field model which
describes the shape of the entire spectrum with a single parameter,
the modulation potential. While the usefulness of the force-field
approximation has been confirmed for regular periods of solar
modulation, it was not tested explicitly for disturbed periods, when
GCR are locally modulated by strong interplanetary transients. Here
we use direct measurements of protons and α -particles performed by
the PAMELA space-borne instrument during December 2006, including a
major Forbush decrease, in order to directly test the validity of the
force-field parameterization. We conclude that (1) The force-field
parametrization works very well in describing the energy spectra of
protons and α -particles directly measured by PAMELA outside the Earths
atmosphere; (2) The energy spectrum of GCR can be well parameterized
by the force-field model also during a strong Forbush decrease; (3)
The estimate of the GCR modulation parameter, obtained using data from
the world-wide neutron monitor network, is in good agreement with the
spectra directly measured by PAMELA during the studied interval. This
result is obtained on the basis of a single event analysis, more events
need to be analyzed.
Title: Long-term variation in the Sun's activity caused by magnetic
Rossby waves in the tachocline
Authors: Zaqarashvili, Teimuraz V.; Oliver, Ramon; Hanslmeier, Arnold;
Carbonell, Marc; Ballester, Jose Luis; Gachechiladze, Tamar; Usoskin,
Ilya G.
Bibcode: 2015ApJ...805L..14Z
Altcode: 2015arXiv150502652Z
Long-term records of sunspot number and concentrations of cosmogenic
radionuclides (10Be and 14C) on the Earth reveal the variation of
the Sun's magnetic activity over hundreds and thousands of years. We
identify several clear periods in sunspot, 10Be, and 14C data as
1000, 500, 350, 200, and 100 years. We found that the periods of the
first five spherical harmonics of the slow magnetic Rossby mode in
the presence of a steady toroidal magnetic field of 1200-1300 G in
the lower tachocline are in perfect agreement with the timescales of
observed variations. The steady toroidal magnetic field can be generated
in the lower tachocline either due to the steady dynamo magnetic field
for low magnetic diffusivity or due to the action of the latitudinal
differential rotation on the weak poloidal primordial magnetic field,
which penetrates from the radiative interior. The slow magnetic Rossby
waves lead to variations of the steady toroidal magnetic field in
the lower tachocline, which modulate the dynamo magnetic field and
consequently the solar cycle strength. This result constitutes a key
point for long-term prediction of the cycle strength. According to our
model, the next deep minimum in solar activity is expected during the
first half of this century.
Title: Numerical model for computation of effective and ambient
dose equivalent at flight altitudes. Application for dose assessment
during GLEs
Authors: Mishev, Alexander; Usoskin, Ilya
Bibcode: 2015JSWSC...5A..10M
Altcode:
A numerical model for assessment of the effective dose and ambient dose
equivalent produced by secondary cosmic ray particles of galactic and
solar origin at commercial aircraft altitudes is presented. The model
represents a full chain analysis based on ground-based measurements
of cosmic rays, from particle spectral and angular characteristics to
dose estimation. The model is based on newly numerically computed
yield functions and realistic propagation of cosmic ray in the
Earth magnetosphere. The yield functions are computed using a
straightforward full Monte Carlo simulation of the atmospheric
cascade induced by primary protons and α-particles and subsequent
conversion of secondary particle fluence (neutrons, protons, gammas,
electrons, positrons, muons and charged pions) to effective dose or
the ambient dose equivalent. The ambient dose equivalent is compared
with reference data at various conditions such as rigidity cut-off
and level of solar activity. The method is applied for computation
of the effective dose rate at flight altitude during the ground level
enhancement of 13 December 2006. The solar proton spectra are derived
using neutron monitor data. The computation of the effective dose
rate during the event explicitly considers the derived anisotropy
i.e. the pitch angle distribution as well as the propagation of the
solar protons in the magnetosphere of the Earth.
Title: Level and length of cyclic solar activity during the Maunder
minimum as deduced from the active-day statistics
Authors: Vaquero, J. M.; Kovaltsov, G. A.; Usoskin, I. G.; Carrasco,
V. M. S.; Gallego, M. C.
Bibcode: 2015A&A...577A..71V
Altcode: 2015arXiv150307664V
Aims: The Maunder minimum (MM) of greatly reduced solar activity
took place in 1645-1715, but the exact level of sunspot activity is
uncertain because it is based, to a large extent, on historical generic
statements of the absence of spots on the Sun. Using a conservative
approach, we aim to assess the level and length of solar cycle during
the MM on the basis of direct historical records by astronomers of that
time.
Methods: A database of the active and inactive days (days
with and without recorded sunspots on the solar disc) is constructed
for three models of different levels of conservatism (loose, optimum,
and strict models) regarding generic no-spot records. We used the
active day fraction to estimate the group sunspot number during the
MM.
Results: A clear cyclic variability is found throughout
the MM with peaks at around 1655-1657, 1675, 1684, 1705, and possibly
1666, with the active-day fraction not exceeding 0.2, 0.3, or 0.4
during the core MM, for the three models. Estimated sunspot numbers
are found to be very low in accordance with a grand minimum of solar
activity.
Conclusions: For the core MM (1650-1700), we have
found that (1) A large portion of no-spot records, which correspond to
the solar meridian observations, may be unreliable in the conventional
database. (2) The active-day fraction remained low (below 0.3-0.4)
throughout the MM, indicating the low level of sunspot activity. (3)
The solar cycle appears clearly during the core MM. (4) The length
of the solar cycle during the core MM appears for 9 ± 1 years, but
this is uncertain. (5) The magnitude of the sunspot cycle during MM
is assessed to be below 5-10 in sunspot numbers. A hypothesis of the
high solar cycles during the MM is not confirmed.
Title: Inferring the Structure of the Solar Corona and Inner
Heliosphere During the Maunder Minimum Using Global Thermodynamic
Magnetohydrodynamic Simulations
Authors: Riley, Pete; Lionello, Roberto; Linker, Jon A.; Cliver,
Ed; Balogh, Andre; Beer, Jürg; Charbonneau, Paul; Crooker, Nancy;
DeRosa, Marc; Lockwood, Mike; Owens, Matt; McCracken, Ken; Usoskin,
Ilya; Koutchmy, S.
Bibcode: 2015ApJ...802..105R
Altcode:
Observations of the Sun’s corona during the space era have led to
a picture of relatively constant, but cyclically varying solar output
and structure. Longer-term, more indirect measurements, such as from
10Be, coupled by other albeit less reliable contemporaneous
reports, however, suggest periods of significant departure from this
standard. The Maunder Minimum was one such epoch where: (1) sunspots
effectively disappeared for long intervals during a 70 yr period; (2)
eclipse observations suggested the distinct lack of a visible K-corona
but possible appearance of the F-corona; (3) reports of aurora were
notably reduced; and (4) cosmic ray intensities at Earth were inferred
to be substantially higher. Using a global thermodynamic MHD model,
we have constructed a range of possible coronal configurations for the
Maunder Minimum period and compared their predictions with these limited
observational constraints. We conclude that the most likely state of the
corona during—at least—the later portion of the Maunder Minimum was
not merely that of the 2008/2009 solar minimum, as has been suggested
recently, but rather a state devoid of any large-scale structure,
driven by a photospheric field composed of only ephemeral regions,
and likely substantially reduced in strength. Moreover, we suggest
that the Sun evolved from a 2008/2009-like configuration at the start
of the Maunder Minimum toward an ephemeral-only configuration by the
end of it, supporting a prediction that we may be on the cusp of a
new grand solar minimum.
Title: The impact of geomagnetic spikes on the production rates
of cosmogenic 14C and 10Be in the Earth's
atmosphere
Authors: Fournier, Alexandre; Gallet, Yves; Usoskin, Ilya; Livermore,
Philip W.; Kovaltsov, Gennady A.
Bibcode: 2015GeoRL..42.2759F
Altcode:
We seek corroborative evidence of the geomagnetic spikes detected
in the Near East ca. 980 BC and 890 BC in the records of the past
production rates of the cosmogenic nuclides 14C and
10Be. Our forward modeling strategy rests on global,
time-dependent, geomagnetic spike field models feeding state-of-the-art
models of cosmogenic nuclide production. We find that spike models with
an energy budget in line with presently inferred large-scale flow at
Earth's core surface fail to produce a visible imprint in the nuclide
record. Spike models able to reproduce the intensity changes reported
in the Near East require an unaccountably high-magnitude core flow,
yet their computed impact on cosmogenic isotope production rates
remains ambiguous. No simple and unequivocal agreement is obtained
between the observed and modeled nuclide records at the epochs of
interest. This indicates that cosmogenic nuclides cannot immediately
be used to confirm the occurrence of these two geomagnetic spikes.
Title: Solar surface rotation: N-S asymmetry and recent speed-up
Authors: Zhang, L.; Mursula, K.; Usoskin, I.
Bibcode: 2015A&A...575L...2Z
Altcode: 2015arXiv150102698Z
Context. The relation between solar surface rotation and sunspot
activity is still not fully resolved. The sunspot activity has
been significantly reduced in solar cycle 24, and several solar
activity indices and flux measurements experienced unprecedentedly
low levels during the last solar minimum.
Aims: We aim to
reveal the momentary variation of solar surface rotation, especially
during the recent years of reduced solar activity.
Methods:
We used a dynamic, differentially rotating reference system to
determine the best-fit annual values of the differential rotation
parameters of active longitudes of solar X-ray flares and sunspots
in 1977-2012.
Results: The evolution of the rotation of solar
active longitudes obtained from observing X-ray flares and sunspots is
very similar. Both hemispheres have increased their rotation rate since
the late 1990s, with the southern hemisphere rotating slightly faster
than the north. In the 1980s, rotation in the northern hemisphere
was considerably faster, but it experienced a major decrease in
the early 1990s. On the other hand, little change was found in the
rotation of the southern hemisphere during these decades. This led
to a positive asymmetry in the north-south rotation rate in the early
part of the time interval studied.
Conclusions: The rotation of
both hemispheres has been speeding up at roughly the same rate since
the late 1990s, with the southern hemisphere rotating slightly faster
than the northern hemisphere. This period coincides with the start of
a significant weakening of the solar activity, as observed in sunspots
and several other solar, interplanetary, and geomagnetic parameters.
Title: An Unusual Pattern of Cosmic-Ray Modulation During Solar
Cycles 23 and 24
Authors: Pacini, A. A.; Usoskin, I. G.
Bibcode: 2015SoPh..290..943P
Altcode: 2014SoPh..tmp..195P
By means of an analysis of data from eight neutron monitor (NM)
stations with different geomagnetic cutoff rigidities, we found an
unusual latitudinal effect observed in the cosmic-ray (CR) modulation
during the last solar cycles. Since the beginning of the ground-based
cosmic-ray monitoring, it is known that the solar-cycle modulation
is more evident in data from high latitude than from the medium
and low latitudes, showing an expected geomagnetic cutoff rigidity
effect. However, a more detailed look shows a new latitudinal effect
in cycle 24: while the magnitude of the solar modulation in the
low-latitude data remains the same for the last three solar minima,
the last solar minimum caused a more intense peak in the polar NM
data than in the previous cycles. After correcting the data for
the geomagnetic changes of the period, we found an anomalous solar
modulation in the last cycle. This suggests a weaker heliospheric
modulation at low-energy particles (responsible for the NM counting
in polar sites) now than in the previous cycles, while there is no
significant difference of the modulation for the more energetic part
of the CR spectrum. Our result can be associated with changes of the
solar wind turbulence, which would corroborate some recent studies
about the last solar minimum phase, and indicates that this new solar
modulation feature is still present in the current solar maximum stage.
Title: Solar Cycle in the Heliosphere and Cosmic Rays
Authors: Bazilevskaya, Galina A.; Cliver, Edward W.; Kovaltsov,
Gennady A.; Ling, Alan G.; Shea, M. A.; Smart, D. F.; Usoskin, Ilya G.
Bibcode: 2015sac..book..409B
Altcode:
No abstract at ADS
Title: Computation of dose rate at flight altitudes during ground
level enhancements no. 69, 70 and 71
Authors: Mishev, A. L.; Adibpour, F.; Usoskin, I. G.; Felsberger, E.
Bibcode: 2015AdSpR..55..354M
Altcode:
A new numerical model of estimating and monitoring the exposure
of personnel due to secondary cosmic radiation onboard aircraft,
in accordance with radiation safety standards as well as European
and national regulations, has been developed. The model aims to
calculate the effective dose at flight altitude (39,000 ft) due to
secondary cosmic radiation of galactic and solar origin. In addition,
the model allows the estimation of ambient dose equivalent at typical
commercial airline altitudes in order to provide comparison with
reference data. The basics, structure and function of the model are
described. The model is based on a straightforward full Monte Carlo
simulation of the cosmic ray induced atmospheric cascade. The cascade
simulation is performed with the PLANETOCOSMICS code. The flux of
secondary particles, namely neutrons, protons, gammas, electrons,
positrons, muons and charged pions is calculated. A subsequent
conversion of the particle fluence into the effective dose or ambient
dose equivalent is performed as well as a comparison with reference
data. An application of the model is demonstrated, using a computation
of the effective dose rate at flight altitude during the ground level
enhancements of 20 January 2005, 13 December 2006 and 17 May 2012.
Title: Solar Cycle in the Heliosphere and Cosmic Rays
Authors: Bazilevskaya, Galina A.; Cliver, Edward W.; Kovaltsov,
Gennady A.; Ling, Alan G.; Shea, M. A.; Smart, D. F.; Usoskin, Ilya G.
Bibcode: 2014SSRv..186..409B
Altcode: 2014SSRv..tmp...44B
Manifestations of the 11-year solar cycle and longer time-scale
variability in the heliosphere and cosmic rays are considered. We
briefly review the cyclic variability of such heliospheric parameters
as solar wind speed and density and heliospheric magnetic field, open
magnetic flux and latitude variations of the heliospheric current
sheet. It is discussed whether the local in-situ observation near
Earth can represent the global 3D heliospheric pattern. Variability
of cosmic rays near Earth provides an indirect useful tool to study
the heliosphere. We discuss details of the heliospheric modulation
of galactic cosmic rays, as recorded at and near Earth, and their
relation to the heliospheric conditions in the outer heliosphere. On
the other hand, solar energetic particles can serve as probes for
explosive phenomena on the Sun and conditions in the corona and inner
heliosphere. The occurrence of major solar proton events depicts an
overall tendency to follow the solar cycle but individual events may
appear at different phases of the solar cycle, as defined by various
factors. The solar cycle in the heliosphere and cosmic rays depicts
a complex pattern which includes different processes and cannot be
described by a simple correlation with sunspot number.
Title: Cosmogenic production and climate contributions to nitrate
record in the TALDICE Antarctic ice core
Authors: Poluianov, S.; Traversi, R.; Usoskin, I.
Bibcode: 2014JASTP.121...50P
Altcode:
This paper presents the results of a comparative wavelet coherence
analysis of a multimillennial nitrate record with a number of climatic
and solar activity proxies. Distinguishing between these factors
is important in the view of a possibility of nitrate deposited in a
polar region to represent galactic cosmic ray flux and, consequently,
solar activity. We used the data from the TALDICE drilling project
(Talos Dome, Antarctica), which covers the age range 12,000-700
BP (years before present, i.e. before 1950) and includes records
of nitrate as well as climatic proxies, such as Na+,
Ca2+, MSA (methanesulphonic acid), δ18O,
SO42-. The solar activity series is represented
by reconstructions of the heliospheric modulation parameter from the
14C and 10Be data. We found (1) a confirmation of
multimillennial relation between nitrate and galactic cosmic ray flux;
(2) no clear signature of long-term variations of nitrate transport
from lower latitudes. We suggest that variations in the nitrate record
in the time scale of hundreds-thousands years are most likely caused
by local production, deposition and post-deposition processes.
Title: Cosmogenic Isotope Variability During the Maunder Minimum:
Normal 11-year Cycles Are Expected
Authors: Poluianov, S. V.; Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2014SoPh..289.4701P
Altcode: 2014SoPh..tmp..119P
The amplitude of the 11-year cycle measured in the cosmogenic isotope
10Be during the Maunder Minimum is comparable to that
during the recent epoch of high solar activity. Because of the virtual
absence of the cyclic variability of sunspot activity during the Maunder
Minimum this seemingly contradicts an intuitive expectation that lower
activity would result in smaller solar-cycle variations in cosmogenic
radio-isotope data, or in none, leading to confusing and misleading
conclusions. It is shown here that large 11-year solar cycles in
cosmogenic data observed during periods of suppressed sunspot activity
do not necessarily imply strong heliospheric fields. Normal-amplitude
cycles in the cosmogenic radio-isotopes observed during the Maunder
Minimum are consistent with theoretical expectations because of the
nonlinear relation between solar activity and isotope production. Thus,
cosmogenic-isotope data provide a good tool to study solar-cycle
variability even during grand minima of solar activity.
Title: Fluence Ordering of Solar Energetic Proton Events Using
Cosmogenic Radionuclide Data
Authors: Kovaltsov, G. A.; Usoskin, I. G.; Cliver, E. W.; Dietrich,
W. F.; Tylka, A. J.
Bibcode: 2014SoPh..289.4691K
Altcode: 2014SoPh..tmp..129K
While data on the cosmogenic isotopes 14C and 10Be
made it possible to evaluate extreme solar proton events (SPEs) in
the past, their relation to standard parameters quantifying the SPE
strengths, viz. the integrated fluence of protons with energy above
30 MeV, F30, is ambiguous and strongly depends on the
assumed shape of the energy spectrum. Here we propose a new index,
the integral fluence of an SPE above 200 MeV, F200, which
is related to the production of the cosmogenic isotopes 14C
and 10Be in the Earth atmosphere, independently of the
assumptions on the energy spectrum of the event. The F200
fluence is reconstructed from past cosmogenic isotope data, which
provides an assessment of the occurrence probability density function
for extreme SPEs. In particular, we evaluate that extreme SPEs with
F200>1010 cm−2 occur no more
frequently than once per 10 - 15 kyr.
Title: Release timescales of solar energetic particles in the
low corona
Authors: Agueda, N.; Klein, K. -L.; Vilmer, N.; Rodríguez-Gasén,
R.; Malandraki, O. E.; Papaioannou, A.; Subirà, M.; Sanahuja, B.;
Valtonen, E.; Dröge, W.; Nindos, A.; Heber, B.; Braune, S.; Usoskin,
I. G.; Heynderickx, D.; Talew, E.; Vainio, R.
Bibcode: 2014A&A...570A...5A
Altcode:
Aims: We present a systematic study of the timing and duration of
the release processes of near-relativistic (NR; >50 keV) electrons
in the low corona.
Methods: We analyze seven well-observed
events using in situ measurements by both the ACE and Wind spacecraft
and context electromagnetic observations in soft X-rays, radio, hard
X-rays and white light. We make use of velocity dispersion analysis to
estimate the release time of the first arriving electrons and compare
with the results obtained by using a simulation-based approach,
taking interplanetary transport effects into account to unfold the
NR electron release time history from in situ measurements.
Results: The NR electrons observed in interplanetary space appear
to be released during either short (<30 min) or long (>2
h) periods. The observation of NR electron events showing beamed
pitch-angle distributions (PADs) during several hours is the clearest
observational signature of sustained release in the corona. On the
other hand, the in situ observation of PADs isotropizing in less
than a couple of hours is a clear signature of a prompt release of
electrons in the low corona. Short release episodes appear to originate
in solar flares, in coincidence with the timing of the observed type
III radio bursts. Magnetic connectivity plays an important role. Only
type III radio bursts reaching the local plasma line measured at 1 AU
are found to be related with an associated release episode in the low
corona. Other type III bursts may also have a release of NR electrons
associated with them, but these electrons do not reach L1. Long
release episodes appear associated with signatures of long acceleration
processes in the low corona (long decay of the soft X-ray emission,
type IV radio bursts, and time-extended microwave emission). Type II
radio bursts are reported for most of the events and do not provide
a clear discrimination between short and long release timescales.
Title: A review of Holocene solar-linked climatic variation
on centennial to millennial timescales: Physical processes,
interpretative frameworks and a new multiple cross-wavelet transform
algorithm
Authors: Soon, Willie; Velasco Herrera, Victor M.; Selvaraj, Kandasamy;
Traversi, Rita; Usoskin, Ilya; Chen, Chen-Tung Arthur; Lou, Jiann-Yuh;
Kao, Shuh-Ji; Carter, Robert M.; Pipin, Valery; Severi, Mirko;
Becagli, Silvia
Bibcode: 2014ESRv..134....1S
Altcode:
We report on the existence and nature of Holocene solar and climatic
variations on centennial to millennial timescales. We introduce a new
solar activity proxy, based on nitrate (NO3-)
concentration from the Talos Dome ice core, East Antarctica. We also
use a new algorithm for computing multiple-cross wavelet spectra in
time-frequency space that is generalized for multiple time series
(beyond two). Our results provide a new interpretive framework for
relating Holocene solar activity variations on centennial to millennial
timescales to co-varying climate proxies drawn from a widespread
area around the globe. Climatic proxies used represent variation in
the North Atlantic Ocean, Western Pacific Warm Pool, Southern Ocean
and the East Asian monsoon regions. Our wavelet analysis identifies
fundamental solar modes at 2300-yr (Hallstattzeit), 1000-yr (Eddy),
and 500-yr (unnamed) periodicities, leaves open the possibility
that the 1500-1800-yr cycle may either be fundamental or derived,
and identifies intermediary derived cycles at 700-yr and 300-yr that
may mark rectified responses of the Atlantic thermohaline circulation
to external solar modulation and pacing. Dating uncertainties suggest
that the 1500-yr and 1800-yr cycles described in the literature may
represent either the same or two separate cycles, but in either case,
and irrespective too of whether it is a fundamental or derived mode in
the sense of Dima and Lohmann (2009), the 1500-1800-yr periodicity is
widely represented in a large number of paleoclimate proxy records. It
is obviously premature to reject possible links between changing solar
activity at these multiple scales and the variations that are commonly
observed in paleoclimatic records.
Title: Critical Analysis of a Hypothesis of the Planetary Tidal
Influence on Solar Activity
Authors: Poluianov, S.; Usoskin, I.
Bibcode: 2014SoPh..289.2333P
Altcode: 2014arXiv1401.3547P; 2014SoPh..tmp....5P
The present work is a critical revision of the hypothesis of the
planetary tidal influence on solar activity published by Abreu et
al. (Astron. Astrophys.548, A88, 2012; called A12 here). A12 describes
the hypothesis that planets can have an impact on the solar tachocline
and therefore on solar activity. We checked the procedure and results
of A12, namely the algorithm of planetary tidal torque calculation
and the wavelet coherence between torque and heliospheric modulation
potential. We found that the claimed peaks in long-period range of
the torque spectrum are artefacts caused by the calculation algorithm
(viz. aliasing effect). Also the statistical significance of the
results of the wavelet coherence is found to be overestimated by an
incorrect choice of the background assumption of red noise. Using a
more conservative non-parametric random-phase method, we found that
the long-period coherence between planetary torque and heliospheric
modulation potential becomes insignificant. Thus we conclude that the
considered hypothesis of planetary tidal influence on solar activity
is not based on a solid ground.
Title: Transmission and Emission of Solar Energetic Particles in
Semi-transparent Shocks
Authors: Kocharov, Leon; Laitinen, Timo; Usoskin, Ilya; Vainio, Rami
Bibcode: 2014ApJ...787L..21K
Altcode:
While major solar energetic particle (SEP) events are associated with
coronal mass ejection (CME)-driven shocks in solar wind, accurate SEP
measurements reveal that more than one component of energetic ions
exist in the beginning of the events. Solar electromagnetic emissions,
including nuclear gamma-rays, suggest that high-energy ions could also
be accelerated by coronal shocks, and some of those particles could
contribute to SEPs in interplanetary space. However, the CME-driven
shock in solar wind is thought to shield any particle source beneath the
shock because of the strong scattering required for the diffusive shock
acceleration. In this Letter, we consider a shock model that allows
energetic particles from the possible behind-shock source to appear in
front of the shock simultaneously with SEPs accelerated by the shock
itself. We model the energetic particle transport in directions parallel
and perpendicular to the magnetic field in a spherical shock expanding
through the highly turbulent magnetic sector with an embedded quiet
magnetic tube, which makes the shock semi-transparent for energetic
particles. The model energy spectra and time profiles of energetic
ions escaping far upstream of the shock are similar to the profiles
observed during the first hour of some gradual SEP events.
Title: Evidence for distinct modes of solar activity
Authors: Usoskin, I. G.; Hulot, G.; Gallet, Y.; Roth, R.; Licht, A.;
Joos, F.; Kovaltsov, G. A.; Thébault, E.; Khokhlov, A.
Bibcode: 2014A&A...562L..10U
Altcode: 2014arXiv1402.4720U
Aims: The Sun shows strong variability in its magnetic activity,
from Grand minima to Grand maxima, but the nature of the variability is
not fully understood, mostly because of the insufficient length of the
directly observed solar activity records and of uncertainties related
to long-term reconstructions. Here we present a new adjustment-free
reconstruction of solar activity over three millennia and study its
different modes.
Methods: We present a new adjustment-free,
physical reconstruction of solar activity over the past three millennia,
using the latest verified carbon cycle, 14C production,
and archeomagnetic field models. This great improvement allowed us to
study different modes of solar activity at an unprecedented level of
details.
Results: The distribution of solar activity is clearly
bi-modal, implying the existence of distinct modes of activity. The
main regular activity mode corresponds to moderate activity that varies
in a relatively narrow band between sunspot numbers 20 and 67. The
existence of a separate Grand minimum mode with reduced solar activity,
which cannot be explained by random fluctuations of the regular mode,
is confirmed at a high confidence level. The possible existence of a
separate Grand maximum mode is also suggested, but the statistics is
too low to reach a confident conclusion.
Conclusions: The Sun
is shown to operate in distinct modes - a main general mode, a Grand
minimum mode corresponding to an inactive Sun, and a possible Grand
maximum mode corresponding to an unusually active Sun. These results
provide important constraints for both dynamo models of Sun-like stars
and investigations of possible solar influence on Earth's climate. Data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/562/L10
Title: VizieR Online Data Catalog: Solar activity reconstructed for
3 millennia (Usoskin+, 2014)
Authors: Usoskin, I. G.; Hulot, G.; Gallet, Y.; Roth, R.; Licht, A.;
Joos, F.; Kovaltsov, G. A.; Thebault, E.; Khokhlov, A.
Bibcode: 2014yCat..35629010U
Altcode:
Indices of solar activity reconstructed from 14C using the
m used in the paper. Two indices are provided - the sunspot number
and the cosmic ray modulation potential, both with the 95% confidence
intervals. The data sets are provided with decadal resolution, thus
the individual solar cycles are not resolved. (2 data files).
Title: Analysis of the ground level enhancement on 17 May 2012 using
data from the global neutron monitor network
Authors: Mishev, A. L.; Kocharov, L. G.; Usoskin, I. G.
Bibcode: 2014JGRA..119..670M
Altcode:
We have analyzed the data of the world neutron monitor network for the
first ground level enhancement of solar cycle 24, the ground level
enhancement (GLE) on 17 May 2012. A newly computed neutron monitor
yield function and an inverse method are applied to estimate the energy
spectrum, anisotropy axis direction, and pitch angle distribution of
the high-energy solar particles in interplanetary space. The method
includes the determination of the asymptotic viewing cones of neutron
monitor stations through computations of trajectories of cosmic rays
in a model magnetosphere. The cosmic ray particle trajectories are
determined with the GEANT-based MAGNETOCOSMICS code using Tsyganenko
1989 and International Geomagnetic Reference Field models. Subsequent
calculation of the neutron monitor responses with the model function
is carried out, that represents an initial guess of the inverse
problem. Derivation of the solar energetic particle characteristics
is fulfilled by fitting the data of the global neutron monitor network
using the Levenberg-Marquardt method over the nine-dimensional parameter
space. The pitch angle distribution and rigidity spectrum of high-energy
protons are obtained as function of time in the course of the GLE. The
angular distribution appears quite complicated. It comprises a focused
beam along the interplanetary magnetic field line from the Sun and a
loss-cone feature around the opposite direction, possibly indicative
of the particle transport in interplanetary magnetic field structures
associated with previous coronal mass ejections.
Title: The world-wide neutron monitor network as a toll to detect
solar neutrons: a revisited approach
Authors: Mishev, Alexander; Usoskin, Ilya; Artamonov, Anton; Kovaltsov,
Gennady A.
Bibcode: 2014cosp...40E2127M
Altcode:
When energetic protons are accelerated in solar flares, they may
locally produce secondary neutrons, which can then escape and reach
the Earth. Features of these neutrons carry direct information on the
conditions at the flare site. The main tool to measure solar neutrons on
ground was the world neutron monitor (NM) network, later complemented by
a network of dedicated solar neutron telescopes. Although measurements
of solar neutrons has long history, detailed computation of the specific
yield function of the NM to solar neutrons was somewhat uncertain. Here
we revise the computation of the NM yield function for solar neutrons,
based on new Monte-Carlo simulation of the neutron-induced atmospheric
cascade, and reassess the sensitivity of the world NM network to solar
neutron events.
Title: On the validity of force-field approximation for galactic
cosmic ray spectrum during Forbush decreases using PAMELA data
Authors: Usoskin, Ilya; Kovaltsov, Gennady A.
Bibcode: 2014cosp...40E3446U
Altcode:
Precise measurements of galactic cosmic rays (GCR) are performed
nowadays by space-based instruments, but they are limited in time
from short-time campaigns to a half-solar cycle long PAMELA and a
few-year long AMS-2 space missions. On the other hand, simple model
approximations for the GCR spectrum, modulated by solar magnetic
activity, are used in many practical applications. The most common is
the so-called force-field model, which is often used in such fields as
atmospheric physics, long-term solar studies, etc. The GCR spectrum
is approximated by a prescribed form with the single parameter,
the modulation potential, whose value can be determined from the
ground-based neutron monitor data. In this way, GCR spectrum can
be modelled for the last about 60 years. While the validity of the
force-field model has been confirmed for regular periods of solar
modulation, it was not known if it is still valid during Forbush
decreases, when GCR are locally modulated by strong interplanetary
transients. Accordingly, this led to essential uncertainty in applying
this approach. The recent direct data from PAMELA instrument cover
a major Forbush decrease in December 2006, which makes it possible
to directly test the validity of the force-field model. We made a
detailed study, by fitting the observed daily GCR spectra as measured
by PAMELA during the Forbush decrease, separately for protons and
alpha-particles, and comparing them with the modulation potential values
assessed from the neutron monitor data. We conclude that even during a
strong Forbush decrease, the force-field model based on neutron monitor
data reasonably approximate the actual GCR spectrum at the daily time
scale. This validate the use of the force-field approximation even
during periods of greatly disturbed heliospheric conditions.
Title: New improved reconstruction of solar activity over 3 millennia:
Evidence for distinct solar dynamo modes
Authors: Usoskin, Ilya; Kovaltsov, Gennady; Hulot, Gauthier.; Gallet,
Yves; Roth, Raphael; Licht, Alexis; Joos, Fortunat; Th, E.; Khokhlov,
A.; Kovaltsov, Gennady A.
Bibcode: 2014cosp...40E3445U
Altcode:
The solar magnetic dynamo can operate in distinct modes - a main general
mode, a Grand minimum mode corresponding to an inactive Sun, and a
possible Grand maximum mode corresponding to an unusually active Sun,
as e.g., observed recently. The reality of such mode separation has
recently been the subject of much debate, with different theoretical
speculations discussed. Here we present the first adjustment-free
physical reconstruction of solar activity over the past three
millennia, using the latest carbon cycle, (14) C production and
archeomagnetic field models. This new improved reconstruction shows
that the solar dynamo process indeed switches between different modes,
either corresponding to different regimes of the dynamo or to changes
in the driving parameters. These results provide important constraints
for both dynamo models of Sun-like stars and investigations of possible
solar influence on Earth’s climate.
Title: The unusual solar minimum in relation to the Sun's history
Authors: Usoskin, Ilya
Bibcode: 2014cosp...40E3443U
Altcode:
The recent solar minimum of 2008-2010 was quite unusual for the space
era with the very quiet solar and heliospheric conditions. On the
other hand, such low activity minima are typical in the centennial
and millennial history of the Sun. Here, a review is presented of the
long-term evolution of solar/heliospheric activity as reconstructed
from direct observations and indirect proxy. A special emphasis is
given to the occurrence of Grand minima and maxima on the long-term
scale, and their relation to the heliospheric modulation of cosmic
rays. It is shown that, after the recent Grand maximum of activity,
the Sun is now in the normal mode of activity.
Title: Cosmogenic production vs. climate for the nitrate record in
the TALDICE Antarctic ice core
Authors: Poluianov, Stepan; Usoskin, Ilya; Traversi, Rita
Bibcode: 2014cosp...40E2583P
Altcode:
Reconstructions of solar activity on the multimillennial scale are
based usually on records of two cosmogenic isotopes (14) C and (10) Be,
measured in tree trunks or ice cores. In addition to these well-known
proxies, a chemical tracer was recently proposed (Traversi et al.,
2012), viz. nitrate, measured in an Antarctic ice sheet with moderate
snow deposition rate. Tropo-stratospheric production of nitrate by
cosmic rays is significant in polar regions because of the effect
of energetic galactic cosmic rays. However, some climatic factors
can influence a nitrate record there. Since the strongest source of
nitrate is located at low and middle latitudes as driven by thunderstorm
activity, the possible air transport from the lower latitudes to the
polar region may significantly distort the signal of solar activity
in a nitrate record. The present work is focused on a statistical
study of the relation between the air transport from low and middle
latitudes and the nitrate deposition in the polar region. We used the
data from the TALDICE drilling project (Talos Dome, Antarctica). As
galactic cosmic ray indices we used the reconstructions of heliospheric
moderation parameter based on (14) C from INTCAL09 and (10) Be from
GRIP. The data series cover the age range from 675 till 12000 years BP
(i.e. before 1950). We applied the wavelet coherence analysis to compare
the nitrate series with a number of substances/proxies: Na(+) , Ca(2+)
, MSA (methanesulphonic acid), delta(18) O, no-sea-salt-SO_4(2-) and
reconstructions of heliospheric modulation parameter from the (14) C and
(10) Be records. We found (1) a confirmation that the multimillennial
variability of nitrate is in inverse relation with cosmic ray flux;
(2) no sign of the nitrate transport from lower latitudes to the site
of deposition. This suggests that variations in the nitrate record in
the time scale of hundreds-thousands of years are most likely caused
by local production and deposition processes.
Title: Extreme event of cosmic rays in 775 AD: Data and hypotheses
Authors: Usoskin, Ilya; Kovaltsov, Gennady
Bibcode: 2014cosp...40E3444U
Altcode:
An interesting event has been found recently that took place around 775
AD, as a peak in cosmogenic radionuclides: 14C, 10Be, and 36Cl. Detailed
analysis of annual 14C data measured in several different tree trunks
(from Japan and Europe) as well as in shallow sea coral skeletons
is confirmed by lower resolution data of 10Be and 36Cl in polar ice
cores. While the very existence of the event is beyond any doubts,
its origin is not clear. We overview different hypotheses proposed
as a cause of the event, including a gamma-ray burst, supernova,
cometary impact and extreme solar flare. We discuss several errors made
earlier in evaluating parameters of the event and the corresponding
phenomena. We show that an extreme event in solar energetic particles
remains the most probable reason for the event.
Title: Occurrence Probability of Large Solar Energetic Particle
Events: Assessment from Data on Cosmogenic Radionuclides in Lunar
Rocks
Authors: Kovaltsov, G. A.; Usoskin, I. G.
Bibcode: 2014SoPh..289..211K
Altcode: 2013arXiv1305.5088K
We revisited assessments of the occurrence probability distribution of
large events in solar energetic particles (SEP), based on measurements
of cosmogenic radionuclides in lunar rocks. We present a combined
cumulative occurrence probability distribution of SEP events based
on three timescales: directly measured SEP fluences for the past 60
years; estimates based on the terrestrial cosmogenic radionuclides
10Be and 14C for the multi-millennial (Holocene)
timescale; and cosmogenic radionuclides measured in lunar rocks on a
timescale of up to 1 Myr. These three timescales yield a consistent
distribution. The data suggest a strong roll-over of the occurrence
probability, so that SEP events with a proton fluence with energy
> 30 MeV greater than 1011 (protons cm−2
yr−1) are not expected on a Myr timescale.
Title: High energy particles and aerosol processes in the atmosphere
Authors: Mironova, Irina; Usoskin, Ilya
Bibcode: 2014cosp...40E2114M
Altcode:
The main ionization source of the middle and low Earth atmosphere
is related to energetic particles coming from outer space. Usually
it is ionization from cosmic rays that is always present in the
atmosphere. However, in a case of a very strong solar eruption some
solar energetic particles (SEP) can reach middle/low atmosphere
increasing the ionization rate up to some orders of magnitude at
polar latitudes. By means of case studies of solar protons events
with different energies of particles and their influence on various
atmospheric parameters it was possible to evaluate the effect of solar
(SEP) and galactic (GCR) particles on polar microphysical processes. The
case studies of the extreme SEP events show their possible applications
for natural variations of the aerosol content. Nevertheless, the effect
of the additional ambient air ionization on the aerosol formation is
minor, in comparison with temperature effect, and can take place only in
the cold polar atmospheric conditions. Possible accompanied temperature
decreases can be connected with chemical changes of polar atmosphere
that can be also reason of high energetic particles’ effect.
Title: Method of Express Analysis of Temporal Evolution of the
Spectral and Angular Distributions of Seps during Gles Using NM Data
Authors: Mishev, Alexander; Usoskin, Ilya
Bibcode: 2014cosp...40E2124M
Altcode:
It is important for space weather studies to be estimate radiation
environment during major SEP (solar energetic particle) events. For this
purpose, the main characteristics, viz. spectra and anisotropy of SEPs,
should be derived in near real time. Here we present a method for a
quasi-real time analysis of ground level enhancements using neutron
monitor (NM) data. The method is based on a precise computations of
SEP propagation in the Earth's magnetosphere, namely the assymptotic
cones of acceptance of NM, application of the new computed neutron
monitor yield function and non-linear optimization. Several examples
and a comparison with previously obtained results as well with full
scale modeling are demonstrated.
Title: Temporal Evolution of Spectral and Angular Characteristics
of SEP Particles during Several GLEs of Solar Cycle 23 Derived from
NM Data
Authors: Mishev, Alexander; Usoskin, Ilya; Kocharov, Leon
Bibcode: 2014cosp...40E2126M
Altcode:
High-energy charged particles of solar origin could represent a severe
radiation risk for astronauts and air crew. In addition, they could
disrupt technological systems. When a ground-based neutron monitor
register abrupt increases in solar energetic particles (SEPs),
we observe a special case of solar energetic particle event, a
ground-level enhancement (GLE). In order to derive the spectral and
angular characteristics of GLE particles a precise computation of
solar energetic particle propagation in the Earth's magnetosphere
and atmosphere is necessary. It consists of detailed computation
of assymptotic cones for neutron monitors (NMs) and application
of inverse method using the newly computed neutron monitor yield
function. Assymptotic directions are computed using the Planetocosmics
code and realistic magnetospheric models, namely IGRF as the internal
model and Tsyganenko 89 with the corresponding Kp index as the
external one. The inverse problem solution is performed on the basis
of non-linear least squares method, namely Levenberg-Marqurdt. In the
study presented here, we analyse several major GLEs of the solar cycle
23 as well as the first GLE event of the solar cycle 24, namely GLE69,
GLE70 and GLE 71. The SEP spectra and pitch angle distribution are
obtained at different momenta since the event's onset. The obtained
characteristics are compared with previously reported results. The
obtained results are briefly discussed.
Title: The Disagreement Between Models and Observations of the Cosmic
Ray Latitude Surveys is Solved with New NM Yield Function
Authors: Mishev, Alexander; Usoskin, Ilya; Kovaltsov, Gennady
Bibcode: 2014cosp...40E2125M
Altcode:
A convenient tool to measure cosmic ray (CR) variations in the
vicinity of Earth is the world network of neutron monitors NMs. In
order to derive angular and spectral characteristics of primary
cosmic ray particles, specifically during ground level enhancements
(GLE), a precise information for NM yield function is necessary. A
long-standing problem, over last decades, is the disagreement between
theoretically predicted spatial variability of CR and the directly
measured latitude survey of NM count rate. Here we present a newly
computed yield function of the standard sea-level 6NM64 neutron
monitor for primary proton and alpha nuclei. The computations have
been performed with Planetocosmics and CORSIKA codes using also an
updated information concerning NM registration efficiency. A previously
neglected effect of the geometrical correction of the NM effective
area is considered. This correction enhances the relative impact of
higher-energy cosmic rays, namely with energy above 5-10 GeV/nucleon,
in neutron monitor count rate. This correction allows us to resolve
the long-standing problem of disagreement between the theoretically
calculated spatial variability of cosmic rays over the globe and the
experimentally measured latitude surveys. The newly calculated yield
function, corrected for this geometrical factor is fully consistent with
the experimental latitude surveys performed during three consecutive
solar minima in 1976-77, 1986-87 and 1996-97.
Title: Parameterization of ionization induced in the atmosphere by
precipitating particles
Authors: Artamonov, Anton; Usoskin, Ilya; Kovaltsov, Gennady
Bibcode: 2014cosp...40E.123A
Altcode:
We present a physical model to calculate ionization induced in
the atmosphere by precipitating particles. This model is based on
the Bethe-Bloch equation applied for precipitating particles such
as: electrons, alpha-particles and protons. The energy range of
precipitating particles is up to 5MeV and 80MeV/nuc respectively. This
model provides an easy implementation with a robust realization of model
calculations for a wide range of incident energies of precipitating
particles. This method is limited to the upper-middle atmosphere. An
ionization yield function [see, Usoskin and Kovaltsov, 2006; Usoskin,
Kovaltsov, Mironova, 2010] can be also used in this model, making it
possible to calculate the atmospheric ionization effect of precipitating
particles for the entire atmosphere, dawn to the ground.
Title: Inconsistency of the Wolf sunspot number series around 1848
Authors: Leussu, Raisa; Usoskin, Ilya G.; Arlt, Rainer; Mursula, Kalevi
Bibcode: 2013A&A...559A..28L
Altcode: 2013arXiv1310.8443L
Aims: Sunspot numbers form a benchmark series in many studies,
but may still contain inhomogeneities and inconsistencies. In
particular, an essential discrepancy exists between the two main
sunspot number series, Wolf and group sunspot numbers (WSN and GSN,
respectively), before 1848. The source of this discrepancy has
remained unresolved so far. However, the recently digitized series
of solar observations in 1825-1867 by Samuel Heinrich Schwabe,
who was the primary observer of the WSN before 1848, makes such an
assessment possible.
Methods: We construct sunspot series,
similar to WSN and GSN but using only Schwabe's data. These series,
called here WSN-S and GSN-S, respectively, were compared with the
original WSN and GSN series for the period 1835-1867 for possible
inhomogeneities.
Results: This study supports the earlier
conclusions that the GSN series is more consistent and homogeneous in
the earlier part than the WSN series. We show that: the GSN series is
homogeneous and consistent with the Schwabe data throughout the entire
studied period; the WSN series decreases by roughly 20% around 1848,
which is caused by the change of the primary observer from Schwabe
to Wolf and an inappropriate individual correction factor used for
Schwabe in the WSN; this implies a major inhomogeneity in the WSN,
which needs to be corrected by reducing its values by 20% before 1848;
the corrected WSN series is in good agreement with the GSN series.
Title: Sunspot positions and sizes for 1825-1867 from the observations
by Samuel Heinrich Schwabe
Authors: Arlt, R.; Leussu, R.; Giese, N.; Mursula, K.; Usoskin, I. G.
Bibcode: 2013MNRAS.433.3165A
Altcode: 2013arXiv1305.7400A; 2013MNRAS.tmp.1611A
Samuel Heinrich Schwabe made 8486 drawings of the solar disc with
sunspots in the period from 1825 November 5 to 1867 December 29. We
have measured sunspot sizes and heliographic positions on digitized
images of these drawings. A total of about 135 000 measurements
of individual sunspots are available in a data base. Positions are
accurate to about 5 per cent of the solar radius or to about 3° in
heliographic coordinates in the solar-disc centre. Sizes were given
in 12 classes as estimated visually with circular cursor shapes on
the screen. Most of the drawings show a coordinate grid aligned with
the celestial coordinate system. A subset of 1168 drawings have no
indication of their orientation. We have used a Bayesian estimator
to infer the orientations of the drawings as well as the average
heliographic spot positions from a chain of drawings of several days,
using the rotation profile of the present Sun. The data base also
includes all information available from Schwabe on spotless days.
Title: Eccentric dipole approximation of the geomagnetic field:
Application to cosmic ray computations
Authors: Nevalainen, J.; Usoskin, I. G.; Mishev, A.
Bibcode: 2013AdSpR..52...22N
Altcode:
A comparison of the full IGRF model of the geomagnetic field with two
simplified models, the truncated IGRF and the eccentric dipole model,
is performed. The simplified models were found to provide a reasonable
approximation for the large scale geomagnetic field distribution. In
the application of the simplified geomagnetic models to the shielding
of cosmic rays in the magnetosphere as quantified via the geomagnetic
cut-off rigidity, the eccentric dipole and the truncated IGRF provide
a good large scale view. The use of the simplified model does not
introduce any additional systematic errors at the global scale but
may be a source of moderate uncertainty at the regional scale in the
tropical Atlantic region. This study quantitatively validates the use
of such simplified geomagnetic models when describing the shielding
of cosmic rays in the magnetosphere.
Title: Waldmeier relations and the solar cycle dynamics by the
mean-field dynamos
Authors: Pipin, V. V.; Sokoloff, D. D.; Usoskin, I. G.
Bibcode: 2013IAUS..294..595P
Altcode: 2012arXiv1211.2423P
The long-term variability of the sunspot cycle, as recorded by the Wolf
numbers, are imprinted in different kinds of statistical relations
which relate the cycle amplitudes, duration and shapes. This subject
always gets a special attention because it is important for the solar
activity forecast. We discuss statistical properties of the mean-field
dynamo model with the fluctuating α-effect. Also, we estimate dynamical
properties of the model for the long and short time-scale and compare
it with the dynamics of the sunspot numbers data sets.
Title: Neutron monitor yield function: New improved computations
Authors: Mishev, A. L.; Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2013JGRA..118.2783M
Altcode: 2016arXiv161201498M
A ground-based neutron monitor (NM) is a standard tool to measure
cosmic ray (CR) variability near Earth, and it is crucially important
to know its yield function for primary CRs. Although there are several
earlier theoretically calculated yield functions, none of them agrees
with experimental data of latitude surveys of sea-level NMs, thus
suggesting for an inconsistency. A newly computed yield function of the
standard sea-level 6NM64 NM is presented here separately for primary
CR protons and α-particles, the latter representing also heavier
species of CRs. The computations have been done using the GEANT-4
PLANETOCOSMICS Monte-Carlo tool and a realistic curved atmospheric
model. For the first time, an effect of the geometrical correction of
the NM effective area, related to the finite lateral expansion of the
CR induced atmospheric cascade, is considered, which was neglected in
the previous studies. This correction slightly enhances the relative
impact of higher-energy CRs (energy above 5-10 GeV/nucleon) in NM count
rate. The new computation finally resolves the long-standing problem of
disagreement between the theoretically calculated spatial variability
of CRs over the globe and experimental latitude surveys. The newly
calculated yield function, corrected for this geometrical factor,
appears fully consistent with the experimental latitude surveys of
NMs performed during three consecutive solar minima in 1976-1977,
1986-1987, and 1996-1997. Thus, we provide a new yield function of the
standard sea-level NM 6NM64 that is validated against experimental data.
Title: The AD775 cosmic event revisited: the Sun is to blame
Authors: Usoskin, I. G.; Kromer, B.; Ludlow, F.; Beer, J.; Friedrich,
M.; Kovaltsov, G. A.; Solanki, S. K.; Wacker, L.
Bibcode: 2013A&A...552L...3U
Altcode: 2013arXiv1302.6897U
Aims: Miyake et al. (2012, Nature, 486, 240, henceforth M12)
recently reported, based on 14C data, an extreme cosmic
event in about AD775. Using a simple model, M12 claimed that the event
was too strong to be caused by a solar flare within the standard
theory. This implied a new paradigm of either an impossibly strong
solar flare or a very strong cosmic ray event of unknown origin that
occurred around AD775. However, as we show, the strength of the event
was significantly overestimated by M12. Several subsequent works have
attempted to find a possible exotic source for such an event, including
a giant cometary impact upon the Sun or a gamma-ray burst, but they are
all based on incorrect estimates by M12. We revisit this event with
analysis of new datasets and consistent theoretical modelling.
Methods: We verified the experimental result for the AD775 cosmic
ray event using independent datasets including 10Be series
and newly measured 14C annual data. We surveyed available
historical chronicles for astronomical observations for the period
around the AD770s to identify potential sightings of aurorae borealis
and supernovae. We interpreted the 14C measurements using
an appropriate carbon cycle model.
Results: We show that:
(1) The reality of the AD775 event is confirmed by new measurements
of 14C in German oak; (2) by using an inappropriate
carbon cycle model, M12 strongly overestimated the event's strength;
(3) the revised magnitude of the event (the global 14C
production Q = (1.1 - 1.5) × 108 atoms/cm2)
is consistent with different independent datasets (14C,
10Be, 36Cl) and can be associated with a
strong, but not inexplicably strong, solar energetic particle event
(or a sequence of events), and provides the first definite evidence
for an event of this magnitude (the fluence >30 MeV was about
4.5 × 1010 cm-2) in multiple datasets; (4)
this interpretation is in agreement with increased auroral activity
identified in historical chronicles.
Conclusions: The results
point to the likely solar origin of the event, which is now identified
as the greatest solar event on a multi-millennial time scale, placing
a strong observational constraint on the theory of explosive energy
releases on the Sun and cool stars.
Title: Consistent long-term variation in the hemispheric asymmetry
of solar rotation
Authors: Zhang, L.; Mursula, K.; Usoskin, I.
Bibcode: 2013A&A...552A..84Z
Altcode:
Context. Solar active longitudes and their rotation have been studied
for a long time using various forms of solar activity. However, the
results on the long-term evolution of rotation rates and the hemispheric
asymmetry obtained by earlier authors differ significantly from each
other.
Aims: We aim to find a consistent result on the long-term
migration of active longitudes of sunspots in 1877-2008 separately for
the two hemispheres.
Methods: We used a dynamic, differentially
rotating reference system to determine the best-fit values of the
differential rotation parameters of active longitudes for each year
in 1877-2008. With these parameters we determined the momentary
rotation rates at the reference latitude of 17° and calculated the
non-axisymmetries of active longitudes. We repeated this with five
different fit intervals and two weighting methods and compared the
results.
Results: The evolution of solar surface rotation in
each hemisphere suggests a quasi-periodicity of about 80-90 years. The
long-term variations of solar rotation in the northern and southern
hemisphere have a close anti-correlation, leading to a significant
80-90-year quasi-periodicity in the north-south asymmetry of solar
rotation. The north-south asymmetry of solar rotation is found to have
an inverse relationship with the area of large sunspots. The latitudinal
contrast of differential rotation is also found to be anti-correlated
with the sunspot area. Different fit and weight methods yield similar
results.
Conclusions: Our results give strong evidence for the
anti-correlation of the rotation of the two solar hemispheres. The
long-term oscillation of solar rotation suggests that a systematic
interchange of angular momentum takes place between the two hemispheres
at a period of about 80-90 years.
Title: The first SEPServer event catalogue ~68-MeV solar proton
events observed at 1 AU in 1996-2010
Authors: Vainio, Rami; Valtonen, Eino; Heber, Bernd; Malandraki, Olga
E.; Papaioannou, Athanasios; Klein, Karl-Ludwig; Afanasiev, Alexander;
Agueda, Neus; Aurass, Henry; Battarbee, Markus; Braune, Stephan;
Dröge, Wolfgang; Ganse, Urs; Hamadache, Clarisse; Heynderickx, Daniel;
Huttunen-Heikinmaa, Kalle; Kiener, Jürgen; Kilian, Patrick; Kopp,
Andreas; Kouloumvakos, Athanasios; Maisala, Sami; Mishev, Alexander;
Miteva, Rositsa; Nindos, Alexander; Oittinen, Tero; Raukunen, Osku;
Riihonen, Esa; Rodríguez-Gasén, Rosa; Saloniemi, Oskari; Sanahuja,
Blai; Scherer, Renate; Spanier, Felix; Tatischeff, Vincent; Tziotziou,
Kostas; Usoskin, Ilya G.; Vilmer, Nicole
Bibcode: 2013JSWSC...3A..12V
Altcode:
SEPServer is a three-year collaborative project funded by the seventh
framework programme (FP7-SPACE) of the European Union. The objective
of the project is to provide access to state-of-the-art observations
and analysis tools for the scientific community on solar energetic
particle (SEP) events and related electromagnetic (EM) emissions. The
project will eventually lead to better understanding of the particle
acceleration and transport processes at the Sun and in the inner
heliosphere. These processes lead to SEP events that form one of the key
elements of space weather. In this paper we present the first results
from the systematic analysis work performed on the following datasets:
SOHO/ERNE, SOHO/EPHIN, ACE/EPAM, Wind/WAVES and GOES X-rays. A catalogue
of SEP events at 1 AU, with complete coverage over solar cycle 23,
based on high-energy (~68-MeV) protons from SOHO/ERNE and electron
recordings of the events by SOHO/EPHIN and ACE/EPAM are presented. A
total of 115 energetic particle events have been identified and analysed
using velocity dispersion analysis (VDA) for protons and time-shifting
analysis (TSA) for electrons and protons in order to infer the SEP
release times at the Sun. EM observations during the times of the
SEP event onset have been gathered and compared to the release time
estimates of particles. Data from those events that occurred during
the European day-time, i.e., those that also have observations from
ground-based observatories included in SEPServer, are listed and a
preliminary analysis of their associations is presented. We find that
VDA results for protons can be a useful tool for the analysis of proton
release times, but if the derived proton path length is out of a range
of 1 AU < s ≲ 3 AU, the result of the analysis may be compromised,
as indicated by the anti-correlation of the derived path length and
release time delay from the associated X-ray flare. The average path
length derived from VDA is about 1.9 times the nominal length of
the spiral magnetic field line. This implies that the path length of
first-arriving MeV to deka-MeV protons is affected by interplanetary
scattering. TSA of near-relativistic electrons results in a release
time that shows significant scatter with respect to the EM emissions
but with a trend of being delayed more with increasing distance between
the flare and the nominal footpoint of the Earth-connected field line.
Title: The First Ground Level Enhancement Event of Solar Cycle 24:
Direct Observation of Shock Formation and Particle Release Heights
Authors: Gopalswamy, N.; Xie, H.; Akiyama, S.; Yashiro, S.; Usoskin,
I. G.; Davila, J. M.
Bibcode: 2013ApJ...765L..30G
Altcode: 2013arXiv1302.1474G
We report on the 2012 May 17 ground level enhancement (GLE) event,
which is the first of its kind in solar cycle 24. This is the first GLE
event to be fully observed close to the surface by the Solar Terrestrial
Relations Observatory (STEREO) mission. We determine the coronal mass
ejection (CME) height at the start of the associated metric type
II radio burst (i.e., shock formation height) as 1.38 Rs (from the
Sun center). The CME height at the time of GLE particle release was
directly measured from a STEREO image as 2.32 Rs, which agrees well
with the estimation from CME kinematics. These heights are consistent
with those obtained for cycle-23 GLEs using back-extrapolation. By
contrasting the 2012 May 17 GLE with six other non-GLE eruptions from
well-connected regions with similar or larger flare sizes and CME
speeds, we find that the latitudinal distance from the ecliptic is
rather large for the non-GLE events due to a combination of non-radial
CME motion and unfavorable solar B0 angle, making the connectivity
to Earth poorer. We also find that the coronal environment may play
a role in deciding the shock strength.
Title: A History of Solar Activity over Millennia
Authors: Usoskin, Ilya G.
Bibcode: 2013LRSP...10....1U
Altcode:
Presented here is a review of present knowledge of the long-term
behavior of solar activity on a multi-millennial timescale, as
reconstructed using the indirect proxy method. The concept of solar
activity is discussed along with an overview of the special indices
used to quantify different aspects of variable solar activity, with
special emphasis upon sunspot number.
Title: Calculation of the cosmic ray induced ionization for the
region of Athens
Authors: Makrantoni, P.; Mavromichalaki, H.; Usoskin, I.; Papaioannou,
A.
Bibcode: 2013JPhCS.409a2232M
Altcode:
A complete study of ionization induced by cosmic rays, both solar and
galactic, in the atmosphere, is presented. For the computation of the
cosmic ray induced ionization, the CRII model was used [1] as well
its new version [2] which is extended to the upper atmosphere. In this
work, this model has been applied to the entire atmosphere, i.e. from
atmospheric depth 0 g/cm2, which corresponds to the upper
limit of the atmosphere, to 1025 g/cm2, which corresponds
to the surface. Moreover, an application has been made as a function
of rigidity and latitude, from 0GV or 90° which corresponds to Polar
regions, to 15GV or 0° which corresponds to Equator. Athens corresponds
to 8.53GV rigidity and 38°N latitude. An application has, also, been
made for the different phases of the solar cycle (maximum at the year
2000 and minimum at the year 2010), which coincides with the operational
period of the cosmic ray station of the University of Athens.
Title: Computations of cosmic ray propagation in the Earth's
atmosphere, towards a GLE analysis
Authors: Mishev, A.; Usoskin, I.
Bibcode: 2013JPhCS.409a2152M
Altcode:
Computation of solar energetic particles propagation in the
magnetosphere and atmosphere of the Earth is very important for ground
level enhancement analysis. Detailed simulations of solar energetic
particles events starting from asymptotic direction computation
and NM detector response make it possible to build a strategy for
inverse problem solution i.e. obtaining the characteristics of
solar energetic particles on the basis on ground measurements. In
this study a simulation of cosmic ray atmospheric cascade is carried
out with PLANETOCOSMICS code. Energy spectra of secondary particles,
namely neutrons and protons are obtained at various altitudes in the
rigidity range of 0.7 GV to 1 TV of primary particles. Considering
updated results for NM-64 detection efficiency the specific yield
function for the standard neutron monitor is obtained for vertically
and obliquely incident primary particles. The obtained results and
applications are discussed.
Title: Forecast of the arrival of interplanetary shocks by measuring
cosmic ray fluctuations in the interplanetary medium
Authors: Starodubtsev, S. A.; Grigoryev, V. G.; Usoskin, I. G.
Bibcode: 2013JPhCS.409a2180S
Altcode:
Here we present a method to forecast the arrival of an interplanetary
shock to the Earth's orbit in advance of up to one day, using cosmic
ray fluctuations and solar wind parameters measured onboard the ACE
spacecraft. The method is based on our previous results [1]. By means
of continuous monitoring of the interplanetary space state since April
2010, we conclude that not all shocks can be reliably forecasted by
the method. Only those interplanetary shocks, for which a large flux
of low-energy particles (10 keV - 10 MeV) of solar or interplanetary
origin exists in the upstream region, can be forecasted. This is
typically related to quasi-parallel shocks. In the absence of such
particles, a forecast cannot be made. This is a typical situation
for quasi-perpendicular shocks. Our analysis shows that, on average,
an interplanetary shock can be forecasted for several hours up to one
day, with the probability about 70%.
Title: Hot Precursor Ejecta and Other Peculiarities of the 2012 May
17 Ground Level Enhancement Event
Authors: Gopalswamy, N.; Xie, H.; Nitta, N. V.; Usoskin, I.; Davila,
J. M.
Bibcode: 2012AGUFMSH21A2180G
Altcode:
We report on the first Ground Level Enhancement (GLE) event of Solar
Cycle 24, which occurred on May 17, 2012 from a well-connected region
(NOAA AR 11476, N11W76) on the Sun. There has been a real dearth
of GLE events during cycle 24: even though the Sun has reached its
solar maximum phase, it has produced only this one GLE event. Over the
first 4.5 years of solar cycle 23, there were 5 GLE events, which is
roughly a third of all the events of that cycle. The recent GLE event
was associated with a moderate flare with an X-ray size of only M5.1,
well below the median flare size (X3.8) of cycle 23 GLE events. On
the other hand, the associated CME was very fast (~2000 km/s),
typical of GLE events. During cycle 23, the CME speeds in GLE events
ranged from 1203 km/s to 3675 km/s with an average value of 2083 km/s
(Gopalswamy et al., 2012). The speed of the cycle 24 GLE was measured
accurately because it was a limb event in the SOHO coronagraphic field
of view. The CME was also observed by the STEREO coronagraphs, which
helped derive the initial acceleration as 1.5 km/s/s, which is also
typical of GLE-producing CMEs. We were also able to directly determine
the heliocentric distance of the CME (2.3 solar radii (Rs)) at the
time of the release of GLE particles because there was a STEREO/COR1
image precisely at the time of the particle release. This result
is consistent with what was obtained for the cycle 23 GLE events,
including the distance of the CME at the time of metric type II burst
onset (1.3 Rs), indicating shock formation very close to the Sun
( ~0.3 Rs above the solar surface). We infer that the shock had to
travel an additional 1 Rs before the GLE particles were released. The
CME had a precursor in the form of a hot ejecta some tens of minutes
before the main eruption. The preceding ejecta is termed hot because
it was observed only in the 94 A images obtained by the Solar Dynamics
Observatory (SDO). The 94 A images correspond to coronal a temperature
of ~6MK. The lower temperature images such as at 193 A did not show
the ejecta. The hot ejecta was accelerating and attained a speed
of ~70 km/s before it was blasted by the big GLE-producing CMEs. We
suggest that the hot material of the precursor ejecta might have been
further accelerated by the CME-driven shock resulting in the GLE
event. Reference Gopalswamy, N.,Xie, H., Yashiro, S., Akiyama, S.,
Mäkelä, P., Usoskin, I. G., Properties of Ground Level Enhancement
Events and the Associated Solar Eruptions During Solar Cycle 23,
Space Science reviews, DOI: 10.1007/s11214-012-9890-4
Title: Heliospheric modulation of galactic cosmic rays during grand
solar minima: Past and future variations
Authors: Owens, M. J.; Usoskin, I.; Lockwood, M.
Bibcode: 2012GeoRL..3919102O
Altcode:
Galactic cosmic ray flux at Earth is modulated by the heliospheric
magnetic field. Heliospheric modulation potential, Φ, during grand
solar minima is investigated using an open solar flux (OSF) model with
OSF source based on sunspot number, R, and OSF loss on heliospheric
current sheet inclination. Changing dominance between source and loss
means Φ varies in- (anti-) phase with R during strong (weak) cycles,
in agreement with Φ estimates from ice core records of 10Be
concentration, which are in-phase during most of the last 300 years,
but anti-phase during the Maunder Minimum. Model results suggest
“flat” OSF cycles, such as solar cycle 20 result from OSF source
and loss terms temporarily balancing throughout the cycle. Thus even
if solar activity continues to decline steadily, the long-term drop
in OSF through SC21 to SC23 may plateau during SC24, though reemerge
in SC25 with the inverted phase relation.
Title: Climate and Weather of the Sun - Earth System
Authors: Usoskin, Ilya; Krivova, Natalie
Bibcode: 2012aaa2.book..397U
Altcode:
The Sun is a variable star whose output, including electromagnetic
radiation, magnetic fields and energetic particles varies at different
time scales, from seconds to millennia. Solar variability affects the
interplanetary medium but also planetary environments, including that of
Earth. The state of the near-Earth environment is collectively called
the Space weather, while its long-term changes make the concept of
Space Climate. This forms the field of an interdisciplinary research
focused on a wide range of topics: from solar physics, solar wind,
cosmic rays, to planetary atmospheres and climate. Special emphasis
is paid upon the processes that inter-relate solar variability
and terrestrial environment - the Sun-Earth system. In this work,
we present an overview on the state of the art in the field of the
weather and climate of the Sun-Earth system.
Title: Properties of Ground Level Enhancement Events and the
Associated Solar Eruptions During Solar Cycle 23
Authors: Gopalswamy, N.; Xie, H.; Yashiro, S.; Akiyama, S.; Mäkelä,
P.; Usoskin, I. G.
Bibcode: 2012SSRv..171...23G
Altcode: 2012SSRv..tmp...38G; 2012arXiv1205.0688G
Solar cycle 23 witnessed the most complete set of observations
of coronal mass ejections (CMEs) associated with the Ground Level
Enhancement (GLE) events. We present an overview of the observed
properties of the GLEs and those of the two associated phenomena,
viz., flares and CMEs, both being potential sources of particle
acceleration. Although we do not find a striking correlation between
the GLE intensity and the parameters of flares and CMEs, the solar
eruptions are very intense involving X-class flares and extreme CME
speeds (average ∼2000 km/s). An M7.1 flare and a 1200 km/s CME are
the weakest events in the list of 16 GLE events. Most (80 %) of the CMEs
are full halos with the three non-halos having widths in the range 167
to 212 degrees. The active regions in which the GLE events originate are
generally large: 1290 msh (median 1010 msh) compared to 934 msh (median:
790 msh) for SEP-producing active regions. For accurate estimation of
the CME height at the time of metric type II onset and GLE particle
release, we estimated the initial acceleration of the CMEs using flare
and CME observations. The initial acceleration of GLE-associated CMEs
is much larger (by a factor of 2) than that of ordinary CMEs (2.3
km/s2 vs. 1 km/s2). We confirmed the initial
acceleration for two events for which CME measurements are available
in the inner corona. The GLE particle release is delayed with respect
to the onset of all electromagnetic signatures of the eruptions:
type II bursts, low frequency type III bursts, soft X-ray flares
and CMEs. The presence of metric type II radio bursts some 17 min
(median: 16 min; range: 3 to 48 min) before the GLE onset indicates
shock formation well before the particle release. The release of GLE
particles occurs when the CMEs reach an average height of ∼3.09 R
s (median: 3.18 R s ; range: 1.71 to 4.01
R s ) for well-connected events (source longitude in the
range W20-W90). For poorly connected events, the average CME height at
GLE particle release is ∼66 % larger (mean: 5.18 R s ;
median: 4.61 R s ; range: 2.75-8.49 R s ). The
longitudinal dependence is consistent with shock accelerations because
the shocks from poorly connected events need to expand more to cross
the field lines connecting to an Earth observer. On the other hand, the
CME height at metric type II burst onset has no longitudinal dependence
because electromagnetic signals do not require magnetic connectivity
to the observer. For several events, the GLE particle release is very
close to the time of first appearance of the CME in the coronagraphic
field of view, so we independently confirmed the CME height at particle
release. The CME height at metric type II burst onset is in the narrow
range 1.29 to 1.8 R s , with mean and median values of
1.53 and 1.47 R s . The CME heights at metric type II
burst onset and GLE particle release correspond to the minimum and
maximum in the Alfvén speed profile. The increase in CME speed between
these two heights suggests an increase in Alfvénic Mach number from
2 to 3. The CME heights at GLE particle release are in good agreement
with those obtained from the velocity dispersion analysis (Reames in
Astrophys. J. 693:812, 2009a; Astrophys. J. 706:844, 2009b) including
the source longitude dependence. We also discuss the implications of
the delay of GLE particle release with respect to complex type III
bursts by ∼18 min (median: 16 in; range: 2 to 44 min) for the flare
acceleration mechanism. A similar analysis is also performed on the
delay of particle release relative to the hard X-ray emission.
Title: Nitrate in Polar Ice: A New Tracer of Solar Variability
Authors: Traversi, R.; Usoskin, I. G.; Solanki, S. K.; Becagli, S.;
Frezzotti, M.; Severi, M.; Stenni, B.; Udisti, R.
Bibcode: 2012SoPh..280..237T
Altcode: 2012SoPh..tmp..169T
Knowledge of the long-term variability of solar activity is of
both astrophysical and geoscientific interest. Reconstructions of
solar activity over multiple millennia are traditionally based on
cosmogenic isotopes 14C or 10Be measured in
natural terrestrial archives, but the two isotopes exhibit significant
differences on millennial time scales, so that our knowledge of solar
activity at this time scale remains somewhat uncertain. Here we present
a new potential proxy of solar activity on the centennial-millennial
time scale, based on a chemical tracer, viz. nitrate content in an ice
core drilled at Talos Dome (Antarctica). We argue that this location
is optimal for preserving the solar signal in the nitrate content
during the Holocene. By using the firn core from the same location
we show that the 11-year and Gleissberg cycles are present with the
variability of 10 - 25 % in nitrate content in the pre-industrial
epoch. This is consistent with the results of independent efforts of
modeling HNO3 and NOy in Antarctic near surface
air. However, meteorological noise on the interannual scale makes
it impossible to resolve individual solar cycles. Based on different
processes of formation and transport compared to cosmogenic isotopes,
it provides new, independent insight into long-term solar activity
and helps resolve the uncertainties related to cosmogenic isotopes as
diagnostics of solar activity.
Title: Occurrence of Extreme Solar Particle Events: Assessment from
Historical Proxy Data
Authors: Usoskin, Ilya G.; Kovaltsov, Gennady A.
Bibcode: 2012ApJ...757...92U
Altcode: 2012arXiv1207.5932U
The probability of occurrence of extreme solar particle events (SPEs)
with proton fluence (>30 MeV) F 30 >= 1010
cm-2 is evaluated based on data on the cosmogenic isotopes
14C and 10Be in terrestrial archives covering
centennial-millennial timescales. Four potential candidates with F
30 = (1-1.5) × 1010 cm-2 and no
events with F 30 > 2 × 1010 cm-2
are identified since 1400 AD in the annually resolved 10Be
data. A strong SPE related to the Carrington flare of 1859 AD is not
supported by the data. For the last 11,400 years, 19 SPE candidates
with F 30 = (1-3) × 1010 cm-2
are found and clearly no event with F 30 > 5 ×
1010 cm-2 (50 times the SPE of 1956 February
23) has occurred. These values serve as observational upper limits
on the strength of SPEs on the timescale of tens of millennia. Two
events, ca. 780 and 1460 AD, appear in different data series making
them strong candidates for extreme SPEs. We build a distribution of
the occurrence probability of extreme SPEs, providing a new strict
observational constraint. Practical limits can be set as F 30
≈ 1, 2-3, and 5×1010 cm-2 for occurrence
probabilities ≈10-2, 10-3, and 10-4
yr-1, respectively. Because of the uncertainties, our
results should be interpreted as a conservative upper limit on the SPE
occurrence near Earth. The mean solar energetic particle (SEP) flux
is evaluated as ≈40 (cm2 s)-1, in agreement
with estimates from lunar rocks. On average, extreme SPEs contribute
about 10% to the total SEP fluence.
Title: Preface: Solar Variability, Cosmic Rays and Climate: What's up?
Authors: Usoskin, Ilya G.
Bibcode: 2012AdSpR..50..655U
Altcode:
No abstract at ADS
Title: Estimating the frequency of extremely energetic solar events,
based on solar, stellar, lunar, and terrestrial records
Authors: Schrijver, C. J.; Beer, J.; Baltensperger, U.; Cliver,
E. W.; Güdel, M.; Hudson, H. S.; McCracken, K. G.; Osten, R. A.;
Peter, T.; Soderblom, D. R.; Usoskin, I. G.; Wolff, E. W.
Bibcode: 2012JGRA..117.8103S
Altcode: 2012arXiv1206.4889S; 2012JGRA..11708103S
The most powerful explosions on the Sun - in the form of bright
flares, intense storms of solar energetic particles (SEPs), and fast
coronal mass ejections (CMEs) - drive the most severe space-weather
storms. Proxy records of flare energies based on SEPs in principle
may offer the longest time base to study infrequent large events. We
conclude that one suggested proxy, nitrate concentrations in polar
ice cores, does not map reliably to SEP events. Concentrations of
select radionuclides measured in natural archives may prove useful in
extending the time interval of direct observations up to ten millennia,
but as their calibration to solar flare fluences depends on multiple
poorly known properties and processes, these proxies cannot presently be
used to help determine the flare energy frequency distribution. Being
thus limited to the use of direct flare observations, we evaluate the
probabilities of large-energy solar events by combining solar flare
observations with an ensemble of stellar flare observations. We conclude
that solar flare energies form a relatively smooth distribution from
small events to large flares, while flares on magnetically active,
young Sun-like stars have energies and frequencies markedly in excess
of strong solar flares, even after an empirical scaling with the mean
coronal activity level of these stars. In order to empirically quantify
the frequency of uncommonly large solar flares extensive surveys
of stars of near-solar age need to be obtained, such as is feasible
with the Kepler satellite. Because the likelihood of flares larger
than approximately X30 remains empirically unconstrained, we present
indirect arguments, based on records of sunspots and on statistical
arguments, that solar flares in the past four centuries have likely
not substantially exceeded the level of the largest flares observed
in the space era, and that there is at most about a 10% chance of a
flare larger than about X30 in the next 30 years.
Title: Grand minima of solar activity during the last millennia
Authors: Usoskin, Ilya G.; Solanki, Sami K.; Kovaltsov, Gennady A.
Bibcode: 2012IAUS..286..372U
Altcode:
In this review we discuss the occurrence and statistical properties of
Grand minima based on the available data covering the last millennia. In
particular, we consider the historical record of sunspot numbers
covering the last 400 years as well as records of cosmogenic isotopes
in natural terrestrial archives, used to reconstruct solar activity
for up to the last 11.5 millennia, i.e. throughout the Holocene. Using
a reconstruction of solar activity from cosmogenic isotope data, we
analyze statistics of the occurrence of Grand minima. We find that: the
Sun spends about most of the time at moderate activity, 1/6 in a Grand
minimum and some time also in a Grand maximum state; Occurrence of Grand
minima is not a result of long-term cyclic variations but is defined
by stochastic/chaotic processes; There is a tendency for Grand minima
to cluster with the recurrence rate of roughly 2000-3000 years, with
a weak ~210-yr periodicity existing within the clusters. Grand minima
occur of two different types: shorter than 100 years (Maunder-type)
and long ~150 years (Spörer-type). It is also discussed that solar
cycles (most possibly not sunspots cycle) could exist during the
Grand minima, perhaps with stretched length and asymmetric sunspot
latitudinal distribution. These results set new observational
constraints on long-term solar and stellar dynamo models.
Title: Reconstructing the history of past solar activity
Authors: Usoskin, Ilya
Bibcode: 2012cosp...39.2038U
Altcode: 2012cosp.meet.2038U
While data of directly observed sunspots is available for the
past centuries, longer time series are required for many purposes,
from purely astrophysical (constraints on solar/stellar dynamo) to
geophysical (assessments on possible solar influence on climate). In
order to reconstruct solar activity in the past, one has to use
indirect proxy methods, the most useful being based on cosmogenic
isotope records. Applying this method to data on cosmogenic 14C
and 10Be measured in independently dated natural archives, one can
evaluate long-term variability of solar activity on multi-centennial
time scales. Here I present a brief review of the modern methods of
long-term solar activity reconstruction, with special emphasis upon
separation of Grand minima and maxima of solar activity.
Title: A new model of cosmogenic production of radiocarbon
14C in the atmosphere
Authors: Kovaltsov, Gennady A.; Mishev, Alexander; Usoskin, Ilya G.
Bibcode: 2012E&PSL.337..114K
Altcode: 2012arXiv1206.6974K
We present the results of full new calculation of radiocarbon
14C production in the Earth atmosphere, using a numerical
Monte-Carlo model. We provide, for the first time, a tabulated
14C yield function for the energy of primary cosmic ray
particles ranging from 0.1 to 1000 GeV/nucleon. We have calculated
the global production rate of 14C, which is 1.64 and 1.88
atoms/cm2/s for the modern time and for the pre-industrial
epoch, respectively. This is close to the values obtained from
the carbon cycle reservoir inventory. We argue that earlier models
overestimated the global 14C production rate because of
outdated spectra of cosmic ray heavier nuclei. The mean contribution of
solar energetic particles to the global 14C is calculated
as about 0.25% for the modern epoch. Our model provides a new tool to
calculate the 14C production in the Earth's atmosphere, which
can be applied, e.g., to reconstructions of solar activity in the past.
Title: Middle atmosphere response to the solar cycle in irradiance
and ionizing particle precipitation.
Authors: Semeniuk, Kirill; Usoskin, Ilya; Fomichev, Victor; Melo,
Stella M. L.; McConnell, John; Fu, Chao
Bibcode: 2012cosp...39.1751S
Altcode: 2012cosp.meet.1751S
The impact of NOx and HOx production by three types of energetic
particle precipitation (EPP), high energy electrons, solar proton
events and galactic cosmic rays is examined using a chemistry climate
model. This process study uses ensemble simulations forced by transient
EPP derived from observations, fixed chemical boundary conditions
and fixed seasonally varying sea surface temperatures. We consider
cases with and without solar cycle in irradiance. Our model results
show a wintertime polar stratosphere ozone reduction of between 3%
and 10% in agreement with previous studies. EPP is found to modulate
the radiative solar cycle effect in the middle atmosphere in a
significant way, bringing temperature and ozone variations closer
to observed patterns. The Southern Hemisphere polar vortex undergoes
an intensification from solar minimum to solar maximum instead of a
weakening. This changes the solar cycle variation of the Brewer-Dobson
circulation, with a weakening during solar maxima compared to solar
minima. In response, the tropical tropopause temperature manifests a
statistically significant solar cycle variation resulting in about 4%
more water vapour transported into the lower tropical stratosphere
during solar maxima compared to solar minima. This has implications
for surface temperature variation due to the associated change in
radiative forcing.
Title: Reconstruction of solar modulation parameter for galactic
cosmic rays for the last 70 years
Authors: Usoskin, Ilya; Kovaltsov, Gennady; Bazilevskaya, Galina
Bibcode: 2012cosp...39.2039U
Altcode: 2012cosp.meet.2039U
No abstract at ADS
Title: Nitrate in polar ice as a new index of solar variability
Authors: Traversi, Rita; Usoskin, Ilya; Solanki, Sami K.; Becagli,
Silvia; Frezzotti, Massimo; Severi, Mirko; Stenni, Barbara; Udisti,
Roberto
Bibcode: 2012cosp...39.2001T
Altcode: 2012cosp.meet.2001T
The Sun affects Earth's climate and environment in multiple ways and
on different time scales but understanding if and how the variations
in solar radiative output might drive global climatic change has
revealed to be a complex and controversial issue. In order to address
the question about the Sun's role on the climate in the past, present
and, eventually, in the future, a reliable reconstruction of solar
activity is mandatory. Over millennia time scales, a quantitative
information about past solar activity can only be obtained through
proxies recorded in natural stratified archives (e.g., tree rings or
ice cores), such as the cosmogenic isotopes 14C and 10Be. Nonetheless,
the two isotopes exhibit significant differences on millennial time
scales, making our knowledge of solar activity at this time scale less
certain. Here we present a new potential proxy of solar activity on the
centennial-millennial time scale, namely nitrate content in the TALDICE
ice core (Talos Dome, placeEast Antarctica). Talos Dome site was shown
to be favourably located to minimize possible local climate effects,
which may be dominant in other coastal sites and, due to a sufficiently
high snow accumulation rate throughout the Holocene, such a reversibly
deposited species as nitrate is preserved here (in contrast to inland
Antarctic sites) making it a potential paleomarker. Comparing the
TALDICE nitrate record with the two traditionally used cosmogenic
proxies of solar activity, we observed that a highly significant
agreement on the millennial and multi-millennial time scales over the
Holocene. The relation at centennial time scales is less significant,
likely due to ice core dating uncertainties. No statistical relationship
was found between the nitrate data series and other chemical markers
of local climate/transport. Consequently, the coherence between
nitrate and cosmogenic isotopes univocally suggests a common origin
of their long-term variability. As concerning the more recent times,
we show that the 11-year and Gleissberg cycles are present at a level
of 10-25% in nitrate content in the pre-industrial epoch after the
Maunder minimum, which is in agreement with model results. However, the
``meteorological noise'' on the interannual scale makes it impossible
to resolve individual solar cycles. Since nitrate is characterised by
different processes of formation and transport, compared to cosmogenic
isotopes, we conclude that nitrate in this Antarctic ice core forms
a novel proxy of solar activity on the centennial and longer time
scales and could help in reconciling the discrepancies between the
two cosmogenic isotopes as diagnostics of solar activity.
Title: Variations of the solar cycle profile in a solar dynamo with
fluctuating dynamo governing parameters
Authors: Pipin, V. V.; Sokoloff, D. D.; Usoskin, I. G.
Bibcode: 2012A&A...542A..26P
Altcode: 2011arXiv1112.6218P
Context. Solar cycles vary in their amplitude and shape. There are
several empirical relations between various parameters that link
the cycle's shape and amplitude, foremost these of the Waldmeier
relations.
Aims: The solar cycle is believed to be a result
of the solar dynamo action, therefore these relations require an
explanation in the framework of this theory, which we aim to present
here.
Methods: We related the cycle-to-cycle variability of
solar activity to fluctuations of solar dynamo drivers and primarily
to fluctuations in the parameter responsible for the recovery of
the poloidal magnetic field from the toroidal one. To be specific,
we developed a model in the framework of the mean-field dynamo
based on the differential rotation and α-effect.
Results:
We demonstrate that the mean-field dynamo model, which is based on
a realistic rotation profile and on nonlinearity that is associated
with the magnetic helicity balance, reproduces both qualitatively
and quantitatively the Waldmeier relations observed in sunspot data
since 1750. The model also reproduces more or less successfully other
relations between the parameters under discussion, in particular,
the link between odd and even cycles (Gnevyshev-Ohl rule).
Conclusions: We conclude that the contemporary solar dynamo theory
provides a way to explain the cycle-to-cycle variability of solar
activity as recorded in sunspots.We discuss the importance of the
model for stellar activity cycles which, as known from the data of
the Mount Wilson HK project, which measures the Ca H and K line index
for other stars, demonstrate the cycle-to-cycle variability similar
to solar cycles. Appendix A is available in electronic form at
http://www.aanda.org
Title: Cosmogenic 7Be and 22Na in Finland:
Production, observed periodicities and the connection to climatic
phenomena
Authors: Leppänen, A. -P.; Usoskin, I. G.; Kovaltsov, G. A.;
Paatero, J.
Bibcode: 2012JASTP..74..164L
Altcode:
This study presents theoretical production calculations and time
series analyses of two cosmogenic isotopes, 7Be and
22Na, from the four high-latitude stations of Kotka,
Kajaani, Rovaniemi and Ivalo located in Finland. We used published
results for 7Be but performed full simulations of the
22Na production in atmosphere. For the first time, lookup
tables of 22Na production by cosmic rays in the atmosphere
are presented. In conjunction with calculations using the new model
of 22Na production, the 7Be/22Na
ratios in the atmosphere were also calculated. The wavelet transform
of the 7Be and 22Na time series revealed sets of
periodicities in the 2.5-8 year range. The wavelet coherence method was
used to study coherences between 7Be and 22Na
and 7Be/22Na data and AO, NAO, AMO, QBO and SO
teleconnection indices representing different climatic variations in
Northern Europe. In the wavelet coherence analyses, the 7Be
activities were found to be mainly modulated by NAO and AMO at an
interannual scale, while 22Na activity was found to be
less effected by climatic phenomena. The 7Be coherence
with other indices was intermittent where the coherence with SO was
limited to Ivalo data and in the case of QBO, to Kotka data. The
22Na data was not found to be in coherence with any of the
studied indices. In the 7Be/22Na ratio a clear
seasonal pattern was observed where low 7Be/22Na
ratios were observed during summer and high ratios during winter. This
was speculated to be caused by the height of atmospheric vertical
mixing. During 2006-2011, the 7Be/22Na
ratios from Kotka, Kajaani and Rovaniemi showed variance at
synoptic time scales but were nearly identical at the seasonal
scale. The 7Be/22Na ratio was proposed to be
a radiochronometer to estimate residence times of aerosols carrying
7Be and 22Na.
Title: Cosmogenic isotope 7Be: A case study of depositional
processes in Rio de Janeiro in 2008-2009
Authors: Pacini, A. A.; Usoskin, I. G.; Evangelista, H.; Echer, E.;
de Paula, R.
Bibcode: 2011AdSpR..48..811P
Altcode:
We present here an investigation of the depositional processes
of 7Be-carrying aerosols in the troposphere through an
analysis of the isotope concentration variability measured at Rio
de Janeiro (Brazil) during 2008 and 2009, with weekly resolution. By
adopting a simplified description of the equilibrium scenario in the
troposphere and combining our isotopic data with regional meteorological
parameters and numerical CRAC:Be7 model of cosmogenic production,
it was possible to quantitatively reproduce the observed seasonal
variability and estimate the typical 7Be-aerosols residence
time in the lower troposphere ( tr ∼ 1 day) as well as
the washout coefficient for each season (wet: Λ = 0.029; and dry:
Λ = 0.023 h -1). These results allowed us to discuss the
origin of the seasonal patterns of 7Be concentrations,
indicating that the wet deposition modulation, caused by changes in
the regional weather condition, is the most important forcing in both
seasons. Even an anomaly in isotopic short-term measured variability
can be explained when a detailed air-mass dynamic is considered. Our
results indicate that anomalous events of tropospheric dynamic, such
as occurrence of strong downward air flux, imprint information about
air masses 3-D movement in the near-ground air 7Be data,
making 7Be a useful tracer of its peculiar dynamics at local
and synoptic scales in the troposphere. This study, limited to a single
location and one year time interval, illustrates the potential of the
method. A more detailed general study is planned for the future.
Title: Evolution of the solar irradiance during the Holocene
Authors: Vieira, L. E. A.; Solanki, S. K.; Krivova, N. A.; Usoskin, I.
Bibcode: 2011A&A...531A...6V
Altcode: 2011arXiv1103.4958V
Context. Long-term records of solar radiative output are vital for
understanding solar variability and past climate change. Measurements
of solar irradiance are available for only the last three decades,
which calls for reconstructions of this quantity over longer time
scales using suitable models.
Aims: We present a physically
consistent reconstruction of the total solar irradiance for the
Holocene.
Methods: We extend the SATIRE (Spectral And Total
Irradiance REconstruction) models to estimate the evolution of the
total (and partly spectral) solar irradiance over the Holocene. The
basic assumption is that the variations of the solar irradiance are
due to the evolution of the dark and bright magnetic features on the
solar surface. The evolution of the decadally averaged magnetic flux
is computed from decadal values of cosmogenic isotope concentrations
recorded in natural archives employing a series of physics-based
models connecting the processes from the modulation of the cosmic
ray flux in the heliosphere to their record in natural archives. We
then compute the total solar irradiance (TSI) as a linear combination
of the jth and jth + 1 decadal values of the open magnetic flux. In
order to evaluate the uncertainties due to the evolution of the Earth's
magnetic dipole moment, we employ four reconstructions of the open flux
which are based on conceptually different paleomagnetic models.
Results: Reconstructions of the TSI over the Holocene, each valid for
a different paleomagnetic time series, are presented. Our analysis
suggests that major sources of uncertainty in the TSI in this model
are the heritage of the uncertainty of the TSI since 1610 reconstructed
from sunspot data and the uncertainty of the evolution of the Earth's
magnetic dipole moment. The analysis of the distribution functions
of the reconstructed irradiance for the last 3000 years, which is the
period that the reconstructions overlap, indicates that the estimates
based on the virtual axial dipole moment are significantly lower at
earlier times than the reconstructions based on the virtual dipole
moment. We also present a combined reconstruction, which represents
our best estimate of total solar irradiance for any given time during
the Holocene.
Conclusions: We present the first physics-based
reconstruction of the total solar irradiance over the Holocene, which
will be of interest for studies of climate change over the last 11 500
years. The reconstruction indicates that the decadally averaged total
solar irradiance ranges over approximately 1.5 W/m2 from
grand maxima to grand minima. Appendix A is available in electronic
form at http://www.aanda.orgThe
TSI data is only available at the CDS via anonymous
ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/531/A6
Title: Applications and usage of the real-time Neutron Monitor
Database
Authors: Mavromichalaki, H.; Papaioannou, A.; Plainaki, C.; Sarlanis,
C.; Souvatzoglou, G.; Gerontidou, M.; Papailiou, M.; Eroshenko, E.;
Belov, A.; Yanke, V.; Flückiger, E. O.; Bütikofer, R.; Parisi,
M.; Storini, M.; Klein, K. -L.; Fuller, N.; Steigies, C. T.;
Rother, O. M.; Heber, B.; Wimmer-Schweingruber, R. F.; Kudela, K.;
Strharsky, I.; Langer, R.; Usoskin, I.; Ibragimov, A.; Chilingaryan,
A.; Hovsepyan, G.; Reymers, A.; Yeghikyan, A.; Kryakunova, O.; Dryn,
E.; Nikolayevskiy, N.; Dorman, L.; Pustil'Nik, L.
Bibcode: 2011AdSpR..47.2210M
Altcode:
A high-time resolution Neutron Monitor Database (NMDB) has started
to be realized in the frame of the Seventh Framework Programme of the
European Commission. This database will include cosmic ray data from at
least 18 neutron monitors distributed around the world and operated in
real-time. The implementation of the NMDB will provide the opportunity
for several research applications most of which will be realized in
real-time mode. An important one will be the establishment of an Alert
signal when dangerous solar cosmic ray particles are heading to the
Earth, resulting into ground level enhancements effects registered by
neutron monitors. Furthermore, on the basis of these events analysis,
the mapping of all ground level enhancement features in near real-time
mode will provide an overall picture of these phenomena and will be used
as an input for the calculation of the ionization of the atmosphere. The
latter will be useful together with other contributions to radiation
dose calculations within the atmosphere at several altitudes and will
reveal the absorbed doses during flights. Moreover, special algorithms
for anisotropy and pitch angle distribution of solar cosmic rays,
which have been developed over the years, will also be set online
offering the advantage to give information about the conditions of
the interplanetary space. All of the applications will serve the
needs of the modern world which relies at space environment and will
use the extensive network of neutron monitors as a multi-directional
spectrographic detector. On top of which, the decreases of the cosmic
ray intensity - known as Forbush decreases - will also be analyzed and
a number of important parameters such as galactic cosmic ray anisotropy
will be made available to the users of NMDB. A part of the NMDB project
is also dedicated to the creation of a public outreach website with the
scope to inform about cosmic rays and their possible effects on humans,
technological systems and space-terrestrial environment. Therefore,
NMDB will also stand as an informative gate on space research through
neutron monitor’s data usage.
Title: VizieR Online Data Catalog: Evolution of solar irradiance
during Holocene (Vieira+, 2011)
Authors: Vieira, L. E. A.; Solanki, S. K.; Krivova, N. A.; Usoskin, I.
Bibcode: 2011yCat..35310006V
Altcode: 2011yCat..35319006V
This is a composite total solar irradiance (TSI) time series for 9495BC
to 2007AD constructed as described in Sect. 3.3 of the paper. Since
the TSI is the main external heat input into the Earth's climate
system, a consistent record covering as long period as possible
is needed for climate models. This was our main motivation for
constructing this composite TSI time series. In order to
produce a representative time series, we divided the Holocene into
four periods according to the available data for each period. Table
4 (see below) summarizes the periods considered and the models
available for each period. After the end of the Maunder Minimum we
compute daily values, while prior to the end of the Maunder Minimum
we compute 10-year averages. For the period for which both solar disk
magnetograms and continuum images are available (period 1) we employ
the SATIRE-S reconstruction (Krivova et al. 2003A&A...399L...1K;
Wenzler et al. 2006A&A...460..583W). SATIRE-T (Krivova et
al. 2010JGRA..11512112K) reconstruction is used from the beginning of
the Maunder Minimum (approximately 1640AD) to 1977AD. Prior to 1640AD
reconstructions are based on cosmogenic isotopes (this paper). Different
models of the Earth's geomagnetic field are available before and after
approximately 5000BC. Therefore we treat periods 3 and 4 (before and
after 5000BC) separately. Further details can be found in the paper. We
emphasize that the reconstructions based on different proxies have
different time resolutions. (1 data file).
Title: Global analysis of active longitudes of sunspots
Authors: Zhang, L.; Mursula, K.; Usoskin, I.; Wang, H.
Bibcode: 2011A&A...529A..23Z
Altcode:
Context. Active longitudes have been found in various manifestations
of solar activity. The longitudinal distribution of, e.g., sunspots
and solar X-ray flares shows two persistent preferred longitudes
separated by roughly 180 degrees. We previously studied solar X-ray
flares using an improved version of a dynamic, differentially rotating
coordinate system and found enhanced rotational asymmetry and rotation
parameter values that are consistent for the three classes of X-ray
flares.
Aims: We aim to find the optimal values of rotation
parameters of active longitudes of sunspots for several different
time intervals and separately for the two solar hemispheres.
Methods: We perform a global study of the longitudinal location of
sunspots (all sunspots and first appearance sunspots) using a refined
version of a dynamic, differentially rotating coordinate system.
Results: We find that the rotation parameters for sunspots are in
good agreement with those obtained for X-ray flares using the same
method. The improved method typically finds somewhat faster equatorial
rotation with better accuracy. The improved treatment also leads to
a larger non-axisymmetry. Rotation parameters for all sunspots and
first appearances closely agree with each other, but non-axisymmetry
is systematically larger for all sunspots than for first appearances,
suggesting that strong fields follow more closely the pattern of active
longitudes. The refined method emphasizes hemispheric differences in
rotation. Over the whole interval, the mean rotation in the southern
hemisphere is slower than in the north. We also find significant
temporal variability in the two rotation parameters over the 136-year
interval. Interestingly, the long-term variations (trends and residual
oscillations) in solar rotation are roughly the opposite in the northern
and southern hemispheres.
Conclusions: Rotation parameters vary
differently with time in the northern and southern hemispheres. Both
sunspots and flares strongly suggest that the northern hemisphere
rotated considerably faster but the southern hemisphere slightly slower
than the Carrington rotation rate during the last three solar cycles.
Title: Revisited Sunspot Data: A New Scenario for the Onset of the
Maunder Minimum
Authors: Vaquero, José M.; Gallego, M. C.; Usoskin, Ilya G.;
Kovaltsov, Gennady A.
Bibcode: 2011ApJ...731L..24V
Altcode: 2011arXiv1103.1520V
The Maunder minimum forms an archetype for the Grand minima,
and detailed knowledge of its temporal development has important
consequences for the solar dynamo theory dealing with long-term
solar activity evolution. Here, we reconsider the current paradigm of
the Grand minimum general scenario by using newly recovered sunspot
observations by G. Marcgraf and revising some earlier uncertain data
for the period 1636-1642, i.e., one solar cycle before the beginning
of the Maunder minimum. The new and revised data dramatically change
the magnitude of the sunspot cycle just before the Maunder minimum,
from 60-70 down to about 20, implying a possibly gradual onset of
the minimum with reduced activity started two cycles before it. This
revised scenario of the Maunder minimum changes, through the paradigm
for Grand solar/stellar activity minima, the observational constraint
on the solar/stellar dynamo theories focused on long-term studies and
occurrence of Grand minima.
Title: A review of Space Climate and an introduction to the papers
of the JASTP special issue on Space Climate
Authors: Mursula, Kalevi; Marsh, Dan; Nandy, Dibyendu; Usoskin, Ilya
Bibcode: 2011JASTP..73..179M
Altcode:
No abstract at ADS
Title: Global analysis of active longitudes of solar X-ray flares
Authors: Zhang, L.; Mursula, K.; Usoskin, I.; Wang, H.
Bibcode: 2011JASTP..73..258Z
Altcode:
There is increasing evidence that various manifestations of solar
activity are non-axisymmetric and mainly occur in two preferred
longitude ranges, so called active longitudes. We have earlier
analyzed the longitudinal occurrence of solar X-ray flares observed
by GOES satellites using a specially developed dynamic, differentially
rotating coordinate system. In this frame, the longitude distribution
shows two persistent preferred longitudes separated by about 180
degrees whose strength alternates in time according to the so called
flip-flop phenomenon. Here we make the first global statistical
analysis to find the best fitting values for parameters describing
the differential rotation of active longitudes of X-ray flares. We
find that the new analysis greatly improves the earlier values for
the rotation parameters, making them consistent between the three
different classes of X-ray flares. The improved parameters also yield
a systematically higher level of non-axisymmetry for the longitudinal
distribution, thus increasing the statistical significance of the
existence of active longitudes. Accordingly, a significant amount of
X-ray flares of different classes are produced by the same two active
longitudes. We also find a significant difference between the rotation
rates in the two solar hemispheres, with active longitudes rotating
faster than the Carrington rate in the northern hemisphere and slower
than the Carrington rate in the southern hemisphere.
Title: Solar modulation parameter for cosmic rays since 1936
reconstructed from ground-based neutron monitors and ionization
chambers
Authors: Usoskin, Ilya G.; Bazilevskaya, Galina A.; Kovaltsov,
Gennady A.
Bibcode: 2011JGRA..116.2104U
Altcode:
The differential energy spectrum of galactic cosmic rays near
Earth is often parameterized by the force field model with the only
time-dependent parameter, the modulation potential $\phi$. Here we
present a series of reconstructed monthly values of the modulation
potential for the period from July 1936 through December 2009. This
works extends our earlier study by employing new data and improving
the reconstruction method. The presented series is a composite of three
parts. The most reliable part is based on data from the world network of
sea level neutron monitors and covers the period since April 1964. The
part between February 1951 and March 1964 is based on data from one
to two mountain neutron monitors of IGY type and is characterized by
larger uncertainties and possible systematic error. The part related
to the period before 1951 is based on data from Forbush ground-based
ionization chambers and is characterized by large uncertainties and
should be taken with caveats. The reconstructed series has been tested
against long-term data of balloon-borne measurements of flux of cosmic
ray ionizing radiation in the stratosphere performed by the Lebedev
Institute since 1957. The comparison shows good agreement since 1964
but suggests that the result before 1964 may contain larger errors
in that the NM-based reconstruction method may underestimate the low
energy part of GCR spectrum.
Title: Solar modulation of cosmic rays since 1936: Neutron monitors
and balloon-borne data
Authors: Usoskin, Ilya
Bibcode: 2011ICRC...11...39U
Altcode: 2011ICRC...32k..39U
No abstract at ADS
Title: Numerical model of cosmic ray induced ionization in the
atmosphere CRAC:CRII
Authors: Usoskin, Ilya
Bibcode: 2011ICRC...11..343U
Altcode: 2011ICRC...32k.343U
No abstract at ADS
Title: Long term Solar/heliospheric variability
Authors: Usoskin, Ilya
Bibcode: 2011ICRC...12..131U
Altcode: 2011ICRC...32l.131U
No abstract at ADS
Title: Long-term variation of solar surface differential rotation
Authors: Zhang, L.; Mursula, K.; Usoskin, I.; Wang, H.; Du, Z.
Bibcode: 2011ASInC...2..175Z
Altcode:
Recently, the surface differential rotation parameters were found to
vary differently with time for the northern and southern hemispheres of
the Sun. Both sunspots and flares strongly suggest that the northern
hemisphere rotated considerably faster than the southern during the
last three solar cycles, showing a strong north-south asymmetry in
solar surface rotation. In order to study the long-term variation of
solar surface differential rotation, the location of sunspots during
1877-2009 is analyzed separately in the two hemispheres. The
variation of the rotation of the northern hemisphere is found to have an
anti-correlation with that of the southern hemisphere and the variation
suggests a period of 10-12 cycles.
Title: Cosmic rays and climate forcing .
Authors: Usoskin, I. G.
Bibcode: 2011MmSAI..82..937U
Altcode:
An important factor affecting the terrestrial environment is the
flux of cosmic rays permanently impinging on Earth. Energetic cosmic
rays initiate a nucleonic-electromagnetic cascade in the atmosphere,
affecting its physical-chemical properties. In particular, cosmic
rays form the dominant source of ionization in the lower and middle
atmosphere. Therefore, a detailed knowledge of processes leading to the
cosmic ray induced ionization makes a solid basis for a quantitative
study of the outer space influence upon Earth. Via the variable
heliospheric modulation of cosmic rays, this provides an indirect
solar-terrestrial link. We present here a review of atmospheric
effects of cosmic rays, including ionization and aerosol particle
formation. Both physical modeling and phenomenological relations are
considered on different time scales.
Title: Cosmogenic 7Be in air: A complex mixture of
production and transport
Authors: Leppänen, A. -P.; Pacini, A. A.; Usoskin, I. G.; Aldahan,
A.; Echer, E.; Evangelista, H.; Klemola, S.; Kovaltsov, G. A.; Mursula,
K.; Possnert, G.
Bibcode: 2010JASTP..72.1036L
Altcode:
The long-time series of 7Be activity in surface air have
been studied with the wavelet analysis technique in order to find
coherence between 7Be activity, theoretical production
in the troposphere and climatic indices. The 7Be activity
were obtained from five different locations, Angra in the tropics in
Brazil, Skåne in mid-latitudes in Southern Sweden, Kiruna in Polar
region in Northern Sweden, Loviisa in Southern Finland and Rovaniemi
in polar region in Northern Finland. The 7Be data from the
Northern hemisphere sites where tested for coherence with theoretical
production of the isotope in troposphere and with the North Atlantic
Oscillation index. In the Southern hemisphere separate theoretical
production was calculated in order to describe local production and
Southern Annular Mode was used as the climatic index. Consistent and
significant coherence were found with theoretical production at Skåne,
Kiruna and Loviisa at time-scales of four years or longer. At Angra
and Rovaniemi sites, no coherence was detected between 7Be
theoretical tropospheric production and measured activity at ground
level. The coherence between 7Be data from Skåne and
Angra and climatic indices is insignificant while data from Northern
and Eastern Scandinavia show clear coherence with climatic indices
at time-scales of four years or longer. Additionally, significant
coherence was found between the cosmic ray induced production and NAO
at the time band of 8-12 years whereas the coherence between cosmic
ray induced production and SAM was insignificant. This feature implies
that the ground level 7Be activity contain mixed information
on both production and transport. This conclusion means that further
evaluation through models which enable accurate realistic models that
will be investigated in future studies.
Title: Fluctuations of energetic particle flux during solar cycle
based on measurements in the solar wind, in the magnetosphere,
and at Earth
Authors: Starodubtsev, S. A.; Usoskin, I. G.
Bibcode: 2010AstL...36..438S
Altcode: 2010PAZh...36..462S
We present the results of our studies of the cosmic-ray fluctuations
in the frequency range 10-4-1.67 × 10-3 Hz
based on energetic particle flux measurements on spacecraft in the
solar wind, in the magnetosphere, and at Earth in the 11-year solar
cycle. The cosmic-ray fluctuation spectrum is shown to have an 11-year
modulation related to the solar cycle. A different behavior of the
level of energetic particle fluctuations measured in different regions
of space is observed for cosmic rays of different origins. We conclude
that the new, previously unknown phenomenon of 11-year modulation of
the cosmic-ray fluctuation spectrum has been established. A possible
explanation of this phenomenon is given.
Title: Cosmic ray induced ionization model CRAC:CRII: An extension
to the upper atmosphere
Authors: Usoskin, Ilya G.; Kovaltsov, Gennady A.; Mironova, Irina A.
Bibcode: 2010JGRD..11510302U
Altcode:
A new version of the CRAC:CRII model computing ionization induced by
cosmic rays in the atmosphere is presented, which is extended to the
upper atmosphere and can be now applied to the entire atmosphere. The
model is able to compute the ionization rate in the atmosphere at
any given location and time provided the energy spectrum of incoming
cosmic rays is known. It is discussed that the use of earlier models,
either analytical or Monte Carlo, with the limited upper energy of
500 MeV, is well validated for the upper atmosphere (above a few
g/cm2 atmospheric depth, which corresponds to the altitude
about 40 km) to study the effect of solar energetic particles but may
lead to a significant underestimate of the background ionization due
to galactic cosmic rays. The use of a full model accounting for the
atmospheric cascade and full energy range of incoming cosmic rays,
rather than earlier simplified models, is recommended to study the
ionization effects of galactic cosmic rays in the upper atmosphere. On
the other hand, transient strong effects of solar energetic particle
events can be studied using truncated models.
Title: A new 3D numerical model of cosmogenic nuclide 10Be
production in the atmosphere
Authors: Kovaltsov, Gennady A.; Usoskin, Ilya G.
Bibcode: 2010E&PSL.291..182K
Altcode:
A new quantitative model of production of the cosmogenic isotope
10Be by cosmic rays in the Earth's atmosphere is
presented. The CRAC:10Be (Cosmic Ray induced Atmospheric Cascade
for 10Be) model is based on a full numerical Monte-Carlo
simulation of the nucleonic-electromagnetic-muon cascade induced by
cosmic rays in the atmosphere and is able to compute the isotope's
production rate at any given 3D location (geographical and altitude)
and time, for all possible parameters including solar energetic particle
events. The model was tested against the results of direct measurements
of the 10Be production in a number of dedicated experiments
to confirm its quantitative correctness. A set of tabulated values
for the yield function is provided along with a detailed numerical
recipe forming a "do-it-yourself" kit, which allows anyone interested
to apply the model for any given conditions. This provides a useful
tool for applying the cosmogenic isotope method in direct integration
with other models, e.g., dynamical atmospheric transport.
Title: Solar modulation in surface atmospheric electricity
Authors: Giles Harrison, R.; Usoskin, Ilya
Bibcode: 2010JASTP..72..176G
Altcode:
The solar wind modulates the flux of galactic cosmic rays impinging
on Earth inversely with solar activity. Cosmic ray ionisation is the
major source of air's electrical conductivity over the oceans and well
above the continents. Differential solar modulation of the cosmic
ray energy spectrum modifies the cosmic ray ionisation at different
latitudes, varying the total atmospheric columnar conductance. This
redistributes current flow in the global atmospheric electrical circuit,
including the local vertical current density and the related surface
potential gradient. Surface vertical current density and potential
gradient measurements made independently at Lerwick Observatory,
Shetland, from 1978 to 1985 are compared with modelled changes in
cosmic ray ionisation arising from solar activity changes. Both the
lower troposphere atmospheric electricity quantities are significantly
increased at cosmic ray maximum (solar minimum), with a proportional
change greater than that of the cosmic ray change.
Title: Sunspot cycles and Grand Minima
Authors: Sokoloff, Dmitry; Arlt, Rainer; Moss, David; Saar, Steven H.;
Usoskin, Ilya
Bibcode: 2010IAUS..264..111S
Altcode:
Observational data concerning the long-term history of cyclic solar
activity as recorded in sunspot and isotopic data are discussed in the
context of solar dynamo theory. In particular, a simple dynamo model
based on differential rotation and the mirror asymmetry of convection
with random fluctuations of dynamo governing parameters is shown to
reproduce some basic features of the solar magnetic activity evolution.
Title: Atmospheric data over a solar cycle: no connection between
galactic cosmic rays and new particle formation
Authors: Kulmala, M.; Riipinen, I.; Nieminen, T.; Hulkkonen, M.;
Sogacheva, L.; Manninen, H. E.; Paasonen, P.; Petäjä, T.; Dal Maso,
M.; Aalto, P. P.; Viljanen, A.; Usoskin, I.; Vainio, R.; Mirme, S.;
Mirme, A.; Minikin, A.; Petzold, A.; Hõrrak, U.; Plaß-Dülmer, C.;
Birmili, W.; Kerminen, V. -M.
Bibcode: 2010ACP....10.1885K
Altcode: 2009ACPD....921525K
Aerosol particles affect the Earth's radiative balance by directly
scattering and absorbing solar radiation and, indirectly, through
their activation into cloud droplets. Both effects are known
with considerable uncertainty only, and translate into even bigger
uncertainties in future climate predictions. More than a decade ago,
variations in galactic cosmic rays were suggested to closely correlate
with variations in atmospheric cloud cover and therefore constitute
a driving force behind aerosol-cloud-climate interactions. Later,
the enhancement of atmospheric aerosol particle formation by ions
generated from cosmic rays was proposed as a physical mechanism
explaining this correlation. Here, we report unique observations on
atmospheric aerosol formation based on measurements at the SMEAR II
station, Finland, over a solar cycle (years 1996-2008) that shed new
light on these presumed relationships. Our analysis shows that none
of the quantities related to aerosol formation correlates with the
cosmic ray-induced ionisation intensity (CRII). We also examined the
contribution of ions to new particle formation on the basis of novel
ground-based and airborne observations. A consistent result is that
ion-induced formation contributes typically significantly less than
10% to the number of new particles, which would explain the missing
correlation between CRII and aerosol formation. Our main conclusion is
that galactic cosmic rays appear to play a minor role for atmospheric
aerosol formation events, and so for the connected aerosol-climate
effects as well.
Title: Critical Comment on the Article by R. Rek ``The Maunder
Minimum and the Sun as the Possible Source of Particles Creating
Increased Abundance of the 14C Carbon Isotope''
Authors: Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2010SoPh..261..353U
Altcode: 2010SoPh..tmp...10U
Several strong but erroneous statements were made by R. Rek in an
article published in this volume of Solar Physics. Here we show that
these misleading statements are caused by neglecting the known effects
of the carbon cycle and misinterpretation of the data. In particular we
show that the claim of the Maunder minimum being "the period without a
significant cessation of activity" contradicts the bulk of observational
evidence and is caused by the misinterpretation of proxy data.
Title: Study of air mass dynamics using beryllium-7 data from Rio
de Janeiro State
Authors: Pacini, Alessandra; Usoskin, Ilya; Evangelista, Heitor;
de Paula, Raquel; Echer, Ezequiel
Bibcode: 2010cosp...38..166P
Altcode: 2010cosp.meet..166P
We present here a study of the atmospheric 7 Be inter-annual
variability measured at Rio de Janeiro (Brazil) and its relation to
local air mass dynamics. 7 Be is a cosmogenic isotope (produced by
the spallation of atmospheric oxygen and nitrogen by cosmic rays)
with the half-life of 53.2 days. Atmospheric concentration of this
cosmogenic radionuclide is highest around 20 km above the surface and
decreases with the altitude. After its production in the atmosphere,
the 7 Be gets attached predominantly to small aerosols and follows
their transport and deposition process. Therefore, temporal variations
of the near-surface atmospheric 7 Be can provide information on the
air mass dynamics, stratosphere-troposphere coupling and cosmic ray
variations. Considering that the production variability is expected
to be small at this location and timescale, we concentrate on the
influence of the atmospheric dynamics and the local climatic upon our
isotopic data. The 7 Be concentration time series was obtained by our
team through nearly continuous weekly air sampling made since August
2008 in Rio de Janeiro (22° 33'S 43° 18'W; Pc=10,89 GV). We have
compared our measured isotopic data with the local climatic indices
(temperature, barometric pressure and precipitation) to understand
the seasonal behavior. In addition, we have applied two theoretical
models to identify the origin of some 7 Be anomalies in our data. Using
these models together we could calculate the 7 Be production (using
the CRAC:Be7 model) in each point of the air sample path (the air mass
back trajectories was calculated using the HYSPLIT model) before the
measurement. Our results show that, during its movement (vertical or
horizontal) into the low atmosphere, the traced air sample experiences
consequent enrichments and losses of the isotopic concentration,
imprinting this information over the surface 7 Be data, and making it
an useful tracer of the atmospheric dynamics.
Title: WWW.NMDB.EU: The real-time Neutron Monitor databas
Authors: Klein, Karl-Ludwig; Steigies, Christian; Steigies, Christian
T.; Wimmer-Schweingruber, Robert F.; Kudela, Karel; Strharsky, Igor;
Langer, Ronald; Usoskin, Ilya; Ibragimov, Askar; Flückiger, Erwin
O.; Bütikofer, Rolf; Eroshenko, Eugenia; Belov, Anatoly; Yanke,
Victor; Klein, Karl-Ludwig; Fuller, Nicolas; Mavromichalaki, Helen;
Papaioannou, Athana-Sios; Sarlanis, Christos; Souvatzoglou, George;
Plainaki, Christina; Geron-Tidou, Maria; Papailiou, Maria-Christina;
Mariatos, George; Chilingaryan, Ashot; Hovsepyan, G.; Reymers, Artur;
Parisi, Mario; Kryakunova, Olga; Tsepakina, Irina; Nikolayevskiy,
Nikolay; Dor-Man, Lev; Pustil'Nik, Lev; García-Población, Oscar
Bibcode: 2010cosp...38.1685K
Altcode: 2010cosp.meet.1685K
The Real time database for high-resolution neutron monitor
measurements(NMDB), which was supported by the 7th Framework
Programme of the European Commission, hosts data on cosmic rays in
the GeV range from European and some non-European neutron monitor
stations. Besides real-time data and historical data over several
decades in a unified format, it offers data products such as galactic
cosmic ray spectra and applications including solar energetic particle
alerts and the calculation of ionisation rates in the atmosphere and
effective radiation dose rates at aircraft altitudes. Furthermore
the web site comprises public outreach pages in several languages
and offers training material on cosmic rays for university students
and researchers and engineers who want to become familiar with cosmic
rays and neutron monitor measurements. This contribution presents an
overview of the provided services and indications on how to access the
database. Operators of other neutron monitor stations are welcome to
submit their data to NMDB.
Title: Modelling of Cosmic Ray Induced Ionization of Low and Middle
Atmosphere: A Review
Authors: Usoskin, Ilya; Kovaltsov, Gennady
Bibcode: 2010cosp...38.1330U
Altcode: 2010cosp.meet.1330U
Cosmic rays form the main source of the atmospheric ionization in low
and middle atmosphere. A major progress has been recently achieved
in numerical modelling of this process, basing on a full Monte-Carlo
simulation of the complicated cascade initiated by cosmic rays in the
atmosphere. Here we present an overview of the current state of the art
in modelling of cosmic ray induced ionization. We discuss the existing
models and approaches, their inter-comparison, range of validity,
advantages and missing points. We also perform an extensive comparison
between model simulations and direct measurements and provide practical
recommendation for a correct choice of the model parameters.
Title: Regional millennial trend in the cosmic ray induced ionization
of the troposphere
Authors: Usoskin, I. G.; Mironova, I. A.; Korte, M.; Kovaltsov, G. A.
Bibcode: 2010JASTP..72...19U
Altcode:
Long-term trends in the tropospheric cosmic ray induced ionization on
the multi-millennial time scale are studied using the newly released
paleomagnetic reconstruction models. Spatial and temporal variations of
the tropospheric ionization has been computed using the CRAC:CRII model
and applying the paleomagnetic CALS7k.2 reconstruction. It has been
shown that long-term variations of the tropospheric ionization are not
spatially homogeneous, and they are defined not only by solar (i.e.,
covariant with solar irradiance) changes but also by the geomagnetic
field. The dominance of the two effects is geographically separated,
which makes it possible to distinguish between direct and indirect
solar-terrestrial climate effects. Possible climate applications
are considered.
Title: A new 3D numerical model for production of cosmogenic
spallation products (7) Be, (10) Be, (22) Na in the atmosphere
Authors: Usoskin, Ilya; Kovaltsov, Gennady
Bibcode: 2010cosp...38.1754U
Altcode: 2010cosp.meet.1754U
A new quantitative model of production of the cosmogenic isotopes,
produced by spallation of atmospheric constitutes by the nucleonic
component of cosmic rays induced cascade in the Earth's atmosphere
is presented. We presents the results for three cosmogenic isotopes:
7 Be, 10 Be and 22 Na, using the CRAC (Cosmic Ray induced Atmospheric
Cascade) model is based on a full numerical Monte-Carlo simulation of
the nucleonic-electromagnetic-muon cascade induced by cosmic rays in
the atmosphere and is able to compute the isotope's production rate
at any given 3D location (geographical and altitude) and time, for all
possible parameters including solar energetic particle events. The model
was tested against the results of direct measurements of production
of 10 Be and 7 Be in a number of dedicated experiments to confirm
its quantitative correctness. A set of tabulated values for the yield
function is provided along with a detailed numerical recipe forming a
`do-it-yourself' kit, which allows anyone interested to apply the model
for any given conditions. This provides a useful tool for applying
the cosmogenic isotope method in direct integration with other models,
e.g., dynamical atmospheric transport.
Title: Can the solar proxies -cloud cover relationship be mediated
by internal climatic oscillations?
Authors: Voiculescu, Mirela; Usoskin, Ilya
Bibcode: 2010cosp...38.1720V
Altcode: 2010cosp.meet.1720V
Significant correlations have been found at global level between
different types of cloud cover and ultraviolet irradiance (UVI),
and respectively cosmic ray induced ionization (CRII). Clouds play
an important role in climate changes as a major contributor to the
Earth's radiation budget. Accordingly, the background conditions when
the cloud-solar relation can contribute to climate change need to
be studied as thoroughly as possible. In our previous work we have
shown that different solar drivers seem to play different roles
in the occurrence of clouds at different altitudes. We found that
the response of clouds to solar drivers is complex, as expected,
but different mechanisms might be at work at different timescales,
depending on cloud characteristics (height and formation) as well as
on general climatic background, geographical position, latitude and
season. On the other hand, it has been shown that solar signal can be
noticed in different teleconnection indices, as for instance NAO. We aim
here at investigating the complicated spatial and temporal relationship
between teleconnection indices (NAO), cloud cover and solar variability
(CR or UVI based).
Title: Variability of Cosmic Ray Induced Ionization Relevant to
Climate: A Review
Authors: Usoskin, Ilya
Bibcode: 2010cosp...38.1718U
Altcode: 2010cosp.meet.1718U
Despite numerous correlative studies relating climatic changes on Earth
to solar variability on different time scales, a physical mechanism
responsible for this is still poorly known. A possible link connecting
solar activity and climate variations is related to cosmic rays and
the physical-chemical changes they produce in the atmosphere. We
review experimental evidence and theoretical grounds for this
relation. We concentrate on two time scales where the effect of cosmic
rays can be disentangled from direct solar effects: long-term scale
(centennial-millennia) and very short time scale (days). We also try to
estimate the expected effect. The cosmic ray-climate link seems to be
a plausible climate driver which operates on different time scales, but
its exact mechanism and relative importance still remain open questions.
Title: Unusual features of solar cycle 23: cosmic rays and solar
wind turbulence.
Authors: Starodubtsev, Sergey; Grigoryev, Vladislav; Usoskin, Ilya;
Mursula, Kalevi; Kovaltsov, Gennady
Bibcode: 2010cosp...38.1679S
Altcode: 2010cosp.meet.1679S
We have analyzed the energetic part of the spectrum of solar wind
turbulence in the frequency range between 2.2 · 10-6 and 1.39 ·
10-4 Hz for the last four solar cycles (1964-2009). We have shown
that the turbulence spectrum of the last cycle No.23 is essentially
different from the three preceding ones Ns.20-22. While the mean power
of fluctuations was roughly constant for the interplanetary magnetic
field strength as well as for the velocity and density of solar wind
plasma, the level of small-scale irregularities of the solar wind was,
and still remains, greatly reduced. We discuss implications of these
peculiar features for the observed variations of cosmic ray intensities
during the solar cycle No.23.
Title: Cosmogenic isotope beryllium-7 in the atmosphere: Production
versus transport
Authors: Pacini, Alessandra; Usoskin, Ilya; Evangelista, Heitor;
Echer, Ezequiel; Mursula, Kalevi; Leppanen, Ari-Pekka
Bibcode: 2010cosp...38..165P
Altcode: 2010cosp.meet..165P
Cosmogenic isotope 7 Be measured near the ground can provide
information about its produc-tion (that occurs in the atmosphere
due to the interaction of cosmic rays and atmospheric constituents)
and its deposition processes (that involves air mass dynamics,
stratosphere-troposphere coupling and local climatic conditions). We
present the results of an investigation of the atmospheric 7 Be
temporal variations at different geographic locations (Finland and
Brazil). This study was based on an analysis of three time series
of 7 Be concentration measured in near-surface air samples from
Rovaniemi and Loviisa (Finland) and Rio de Janeiro (Brazil) for the
last decades. We made use of the wavelet spectral method to identify the
frequency-temporal features of the 7 Be temporal variations that allowed
us to determine the relative importance of production and deposition
process for the observed data. By comparing these time series with
climatic indices and the values of 7 Be concentration expected from
the model for the same period, we found that the climate system is the
main driver of the surface isotopic modulation, while the imprints of
the production variations are geographically dependent. Thus,7 Be can
be considered a good tool to monitor the large-scale air mass dynamics.
Title: Effect of an extreme solar energetic particle event of January
20, 2005 on polar stratospheric aerosols
Authors: Mironova, Irina; Usoskin, Ilya; Kovaltsov, Gennady; Randall,
Cora
Bibcode: 2010cosp...38.1350M
Altcode: 2010cosp.meet.1350M
This work is an extension of a phenomenological study of the middle
polar atmosphere response to a severe solar energetic particle (SEP)
event of January 20, 2005. The present work is focused on evaluation
of the potential influence of atmospheric ionization caused by solar
cosmic rays upon formation of aerosol particles in the low stratosphere
over the polar regions. We have performed a thorough analysis of
variations of the daily profiles of aerosol extinction as measured
by the POAM III instrument in different wavelengths for both North
and South polar regions during January 2005. We found statistically
significant changes in the aerosol parameters associated with the
SEP event that are stronger in the South hemisphere (local austral
summer). The changes are mostly related to ultra-fine and fine aerosols
and show no effect for larger particles.
Title: Ionization of low and middle atmosphere caused by strong
solar particle events
Authors: Usoskin, Ilya; Mironova, Irina; Tylka, Allan J.; Kovaltsov,
Gennady; Dietrich, William F.
Bibcode: 2010cosp...38.1343U
Altcode: 2010cosp.meet.1343U
We quantitatively evaluate the possible ionization effect in the low and
middle atmosphere for the major GLEs (Ground Level Enhancements) of the
last five solar cycles. Reconstruction of the energy spectrum of solar
protons was done based on fits to measurements from ground-based and
satellite-borne instruments covering a wide energy range. Computations
of the atmospheric ionization are based on the numerical 3D CRAC:CRII
model. We show that the direct ionization effect of GLE is negligible or
even negative, due to the accompanying Forbush decreases, in all low-and
mid-latitude regions. The ionization effect is positive only in polar
atmosphere, where it can be dramatic in the upper atmosphere during
major GLE events but quickly fades downwards. We present a Table of
the net ionization effect for all major GLEs of the last solar cycles.
Title: Atmospheric Data over a Solar Cycle: No Connection between
Galactic Cosmic Rays and Particle Formation in Boreal Forest
Authors: Riipinen, I.; Kulmala, M. T.; Nieminen, T.; Hulkkonen, M.;
Sogacheva, L.; Manninen, H.; Paasonen, P.; Petdjd, T. T.; Dal Maso,
M.; Aalto, P.; Viljanen, A.; Usoskin, I.; Vainio, R. O.; Mirme, S.;
Mirme, A.; Minikin, A.; Petzold, A.; Horrak, U.; Plass-Duelmer, C.;
Birmili, W.; Kerminen, V.
Bibcode: 2009AGUFM.A13B0207R
Altcode:
Aerosol particles affect the Earth’s radiative balance by
directly scattering and absorbing solar radiation and, indirectly,
through their activation into cloud droplets. Both effects are known
with considerable uncertainty only, and translate into even bigger
uncertainties in future climate predictions. More than a decade ago,
variations in galactic cosmic rays were suggested to closely correlate
with variations in atmospheric cloud cover and therefore constitute
a driving force behind aerosol-cloud-climate interactions. Later,
the enhancement of atmospheric aerosol particle formation by ions
generated from cosmic rays was proposed as a physical mechanism
explaining this correlation. Here, we report unique observations on
atmospheric aerosol formation based on measurements at the SMEAR II
station, Finland, over a solar cycle (years 1996-2008) that shed new
light on these presumed relationships. Our analysis shows that none
of the quantities related to aerosol formation correlates with the
cosmic ray-induced ionisation intensity (CRII, see Fig. 1). We also
examined the contribution of ions to new particle formation on the
basis of novel ground-based and airborne observations. A consistent
result is that ion-induced formation contributes typically less than
10% to the number of new particles, which would explain the missing
correlation between CRII and aerosol formation. Our main conclusion is
that galactic cosmic rays appear to play a minor role for atmospheric
aerosol formation, and so for the connected aerosol-climate effects
as well. Figure 1. Particle formation events and CRII at the SMEAR II
station in Hyytiälä, Finland during 1996-2008.
Title: Does sunspot number calibration by the “magnetic needle”
make sense?
Authors: Mursula, K.; Usoskin, I.; Yakovchouk, O.
Bibcode: 2009JASTP..71.1717M
Altcode:
It has been suggested recently that early sunspot numbers should be
re-calibrated and significantly corrected using the observed daily
range of the geomagnetic declination (so-called rY values). The
suggested "correction" method makes an a priori detrending of
the rY series and then extends the linear regression between rY
and sunspot numbers established for the last 25 years to earlier
times. The suggested "correction" of sunspot numbers by roughly
30% goes far beyond the traditional estimates of observational
uncertainties of sunspots. Concentrating here on Zürich sunspot
numbers (Rz), we demonstrate that the rY values do not actually imply
that the observed Rz values in the 19th century are systematically
underestimated. Rather, we find that the Rz numbers are fairly uniform
after mid-19th century. The suggested "correction" is largely induced
by the detrending of the rY series, which enhances the rY-based sunspot
activity in the 19th century relative to later times. We also show
that while the annually averaged declinations have a rough relation
between sunspots and other related solar parameters, this relation
is strongly seasonally dependent and, therefore, not sufficiently
accurate or uniform to allow annually averaged rY values to be used
as a very reliable proxy of solar activity in early times.
Title: Dynamics of the Earth's Particle Radiation Environment
Authors: Vainio, Rami; Desorgher, Laurent; Heynderickx, Daniel;
Storini, Marisa; Flückiger, Erwin; Horne, Richard B.; Kovaltsov,
Gennady A.; Kudela, Karel; Laurenza, Monica; McKenna-Lawlor, Susan;
Rothkaehl, Hanna; Usoskin, Ilya G.
Bibcode: 2009SSRv..147..187V
Altcode:
The physical processes affecting the dynamics of the Earth’s particle
radiation environment are reviewed along with scientific and engineering
models developed for its description. The emphasis is on models that
are either operational engineering models or models presently under
development for this purpose. Three components of the radiation
environment, i.e., galactic cosmic rays (GCRs), solar energetic
particles (SEPs) and trapped radiation, are considered separately. In
the case of SEP models, we make a distinction between statistical
flux/fluence models and those aimed at forecasting events. Models
of the effects of particle radiation on the atmosphere are also
reviewed. Further, we summarize the main features of the models and
discuss the main outstanding issues concerning the models and their
possible use in operational space weather forecasting. We emphasize
the need for continuing the development of physics-based models of
the Earth’s particle radiation environment, and their validation
with observational data, until the models are ready to be used for
nowcasting and/or forecasting the dynamics of the environment.
Title: History of cosmic ray research in Finland
Authors: Usoskin, I. G.; Valtonen, E.; Vainio, R.; Tanskanen, P. J.;
Aurela, A. M.
Bibcode: 2009AdSpR..44.1232U
Altcode:
The history of cosmic ray research in Finland can be traced back to
the end of 1950s, when first ground-based cosmic ray measurements
started in Turku. The first cosmic ray station was founded in
Oulu in 1964 performing measurements of cosmic rays by a muon
telescope, which was later complemented by a neutron monitor. Since
the 1990s, several research centers and universities, such as The
Finnish Meteorological Institute, Helsinki University of Technology,
University of Oulu, University of Turku and University of Helsinki have
been involved in space science projects, such as SOHO, AMS, Cluster,
Cassini, BepiColombo, etc. At the same time, ground-based cosmic ray
measurements have reached a new level, including a fully automatic
on-line database in Oulu and a new muon measuring underground site
in Pyhäsalmi. Research groups in Helsinki, Oulu and Turku have also
extensive experience in theoretical investigations of different aspects
of cosmic ray physics. Cosmic ray research has a 50-year long history
in Finland, covering a wide range from basic long-running ground-based
observations to high-technology space-borne instrumentation and
sophisticated theoretical studies. Several generations of researchers
have been involved in the study ensuring transfer of experience and
building the recognized Finnish research school of cosmic ray studies.
Title: A Solar Cycle Lost in 1793-1800: Early Sunspot Observations
Resolve the Old Mystery
Authors: Usoskin, Ilya G.; Mursula, Kalevi; Arlt, Rainer; Kovaltsov,
Gennady A.
Bibcode: 2009ApJ...700L.154U
Altcode: 2009arXiv0907.0063U
Because of the lack of reliable sunspot observations, the quality of
the sunspot number series is poor in the late 18th century, leading
to the abnormally long solar cycle (1784-1799) before the Dalton
minimum. Using the newly recovered solar drawings by the 18-19th
century observers Staudacher and Hamilton, we construct the solar
butterfly diagram, i.e., the latitudinal distribution of sunspots
in the 1790s. The sudden, systematic occurrence of sunspots at high
solar latitudes in 1793-1796 unambiguously shows that a new cycle
started in 1793, which was lost in the traditional Wolf sunspot
series. This finally confirms the existence of the lost cycle that
has been proposed earlier, thus resolving an old mystery. This Letter
brings the attention of the scientific community to the need of revising
the sunspot series in the 18th century. The presence of a new short,
asymmetric cycle implies changes and constraints to sunspot cycle
statistics, solar activity predictions, and solar dynamo theories,
as well as for solar-terrestrial relations.
Title: Correction to ``Stochastic simulation of cosmic ray modulation
including a wavy heliospheric current sheet''
Authors: Alanko-Huotari, K.; Usoskin, I. G.; Mursula, K.; Kovaltsov,
G. A.
Bibcode: 2009JGRA..114.3101A
Altcode: 2009JGRA..11403101A
Abstract Available
from http://www.agu.org
Title: On the common solar signal in different cosmogenic isotope
data sets
Authors: Usoskin, Ilya G.; Horiuchi, Kazuho; Solanki, Sami; Kovaltsov,
Gennady A.; Bard, Edouard
Bibcode: 2009JGRA..114.3112U
Altcode: 2009JGRA..11403112U
In this article, we aim to determine frequency ranges and intervals
of time in which the solar signal dominates in different cosmogenic
isotope data. From a 14C-based reconstruction of cosmic ray
intensity over the last millennia, we computed expected 10Be
variations in two Antarctic sites (Dom Fuji and South Pole) and two
Greenland sites (Dye-3 and GISP-2) and compared them with the actually
measured 10Be abundance at the sites. By applying different
methods of analysis, such as bivariate correlation, conventional
FFT coherence, and wavelet coherence, we found the following: (1)
The modeled series, on the basis of 14C data, are in good
agreement with the measured 10Be data sets, on different
timescales and at different locations, confirming the existence of a
common solar signal in both isotope data. (2) The 10Be data
are driven by the solar signal on timescales from about 100 years up
to 1000 years or even to multimillennial scales (at the longer scales,
paleomagnetism plays an increasingly important role). (3) The local
climate dominates the 10Be data mostly on short (<100
years) timescales, but the solar signal becomes important even at short
scales during periods of Grand minima of solar activity. (4) There is an
indication of a possible systematic uncertainty in the early Holocene,
likely due to a not-perfectly-stable thermohaline circulation, which
requires additional studies. We have shown that both 14C- and
10Be-based records are consistent with each other over a wide
range of timescales and time intervals. They form a robust basis for
quantitative reconstructions of solar activity variations in the past.
Title: Ionization of the earth's atmosphere by solar and galactic
cosmic rays
Authors: Usoskin, Ilya G.; Desorgher, Laurent; Velinov, Peter; Storini,
Marisa; Flückiger, Erwin O.; Bütikofer, Rolf; Kovaltsov, Gennady A.
Bibcode: 2009AcGeo..57...88U
Altcode: 2008AcGeo..57...88U; 2008AcGeo.tmp...40U
A brief review of the research of atmospheric effects of cosmic
rays is presented. Numerical models are discussed, that are capable
to compute the cosmic ray induced ionization at a given location
and time. Intercomparison of the models, as well as comparison with
fragmentary direct measurements of the atmospheric ionization, validates
their applicability for the entire atmosphere and the whole range of the
solar activity level variations. The effect of sporadic solar energetic
particle events is shown to be limited on the global scale, even for
the most severe event, but can be very strong locally in polar regions,
affecting the physical-chemical properties of the upper atmosphere,
especially at high altitudes. Thus, a new methodology is presented to
study cosmic ray induced ionization of the atmosphere in full detail
using realistic numerical models calibrated to direct observations.
Title: Grand Minima of Solar Activity and the Mean-Field Dynamo
Authors: Usoskin, I. G.; Sokoloff, D.; Moss, D.
Bibcode: 2009SoPh..254..345U
Altcode:
We demonstrate that a simple solar dynamo model, in the form of
a Parker migratory dynamo with random fluctuations of the dynamo
governing parameters and algebraic saturation of dynamo action, can
at least qualitatively reproduce all the basic features of solar
Grand Minima as they are known from direct and indirect data. In
particular, the model successfully reproduces such features as an
abrupt transition into a Grand Minimum and the subsequent gradual
recovery of solar activity, as well as mixed-parity butterfly
diagrams during the epoch of the Grand Minimum. The model predicts
that the cycle survives in some form during a Grand Minimum, as well
as the relative stability of the cycle inside and outside of a Grand
Minimum. The long-term statistics of simulated Grand Minima appears
compatible with the phenomenology of the Grand Minima inferred from
the cosmogenic isotope data. We demonstrate that such ability to
reproduce the Grand Minima phenomenology is not a general feature of
the dynamo models but requires some specific assumption, such as random
fluctuations in dynamo governing parameters. In general, we conclude
that a relatively simple and straightforward model is able to reproduce
the Grand Minima phenomenology remarkably well, in principle providing
us with a possibility of studying the physical nature of Grand Minima.
Title: A History of Solar Activity over Millennia
Authors: Usoskin, Ilya G.
Bibcode: 2008LRSP....5....3U
Altcode: 2008arXiv0810.3972U
Presented here is a review of present knowledge of the long-term
behavior of solar activity on a multi-millennial timescale, as
reconstructed using the indirect proxy method.
Title: Variations of aerosol optical properties during the extreme
solar event in January 2005
Authors: Mironova, I. A.; Desorgher, L.; Usoskin, I. G.; Flückiger,
E. O.; Bütikofer, R.
Bibcode: 2008GeoRL..3518610M
Altcode:
We present the results of analysis of the aerosol optical depth
variations for January 2005 when an extreme solar energetic particle
event occurred leading to a greatly enhanced flux of energetic particles
penetrating into the atmosphere. An increase of the concentration
of sulfate or nitrate aerosol was found on the second day after the
solar energetic particle event in the south magnetic pole region
with the maximum penetration of anisotropic solar cosmic rays. This
suggests that an enhanced flux of solar energetic particles can lead
to notable changes in the chemical and physical properties of the polar
troposphere. A statistical test confirms that the observed change of the
aerosol index is significant and is unlikely to be related to a spatial
or temporal independent fluctuation of the aerosol content. Thus, the
results of the present work provide evidence of a direct influence of
cosmic rays on physical-chemical properties of the atmosphere.
Title: Solar Grand Minima and Random Fluctuations in Dynamo Parameters
Authors: Moss, D.; Sokoloff, D.; Usoskin, I.; Tutubalin, V.
Bibcode: 2008SoPh..250..221M
Altcode: 2008arXiv0806.3331M; 2008SoPh..tmp..101M
We consider to what extent the long-term dynamics of cyclic solar
activity in the form of Grand Minima can be associated with random
fluctuations of the parameters governing the solar dynamo. We consider
fluctuations of the alpha coefficient in the conventional Parker
migratory dynamo, and also in slightly more sophisticated dynamo
models, and demonstrate that they can mimic the gross features of the
phenomenon of the occurrence of Grand Minima over suitable parameter
ranges. The temporal distribution of these Grand Minima appears chaotic,
with a more or less exponential waiting time distribution, typical of
Poisson processes. In contrast, however, the available reconstruction of
Grand Minima statistics based on cosmogenic isotope data demonstrates
substantial deviations from this exponential law. We were unable to
reproduce the non-Poissonic tail of the waiting time distribution
either in the framework of a simple alpha-quenched Parker model or in
its straightforward generalization, nor in simple models with feedback
on the differential rotation. We suggest that the disagreement may
only be apparent and is plausibly related to the limited observational
data, and that the observations and results of numerical modeling can
be consistent and represent physically similar dynamo regimes.
Title: Forbush decreases of cosmic rays: Energy dependence of the
recovery phase
Authors: Usoskin, I. G.; Braun, I.; Gladysheva, O. G.; HöRandel,
J. R.; JäMséN, T.; Kovaltsov, G. A.; Starodubtsev, S. A.
Bibcode: 2008JGRA..113.7102U
Altcode: 2008JGRA..11307102U
Cause and general shape of Forbush decreases of cosmic rays
are relatively well understood, however, the knowledge of their
recovery times remains rather poor. Earlier results of theoretical
and fragmentary statistical studies are in disagreement whether
the recovery time does or does not depend on the energy of cosmic
rays. A thorough empirical study of the recovery phase of strong
isolated Forbush decreases is presented here, based on the ground
based data from the World Neutron Monitor Network since 1964 and three
ground based muon telescopes since 1973. In total 39 strong Forbush
decreases, suitable for the analysis, have been identified for the
period 1964-2006, 24 of them depicting a clear energy dependence of
the recovery time and 15 consistent with no energy dependence. All
analyzed Forbush decreases with magnitudes exceeding 10% demonstrate
an energy dependence of the recovery time, while smaller events can
be of either type. No apparent relation between the occurrence of
energy dependent/independent recovery and the IMF polarity has been
found. This result provides an observational constraint for more
detailed modeling of the propagation of interplanetary transients and
their dynamic effects on cosmic ray transport.
Title: Cosmic Ray Induced Ion Production in the Atmosphere
Authors: Bazilevskaya, G. A.; Usoskin, I. G.; Flückiger, E. O.;
Harrison, R. G.; Desorgher, L.; Bütikofer, R.; Krainev, M. B.;
Makhmutov, V. S.; Stozhkov, Y. I.; Svirzhevskaya, A. K.; Svirzhevsky,
N. S.; Kovaltsov, G. A.
Bibcode: 2008SSRv..137..149B
Altcode: 2008SSRv..tmp...44B
An overview is presented of basic results and recent developments
in the field of cosmic ray induced ionisation in the atmosphere,
including a general introduction to the mechanism of cosmic ray
induced ion production. We summarize the results of direct and indirect
measurements of the atmospheric ionisation with special emphasis to
long-term variations. Models describing the ion production in the
atmosphere are also overviewed together with detailed results of
the full Monte-Carlo simulation of a cosmic ray induced atmospheric
cascade. Finally, conclusions are drawn on the present state and further
perspectives of measuring and modeling cosmic ray induced ionisation
in the terrestrial atmosphere.
Title: Reconstruction Of Grand Minima Of Solar Activity On
Multi-Millennial Time Scale
Authors: Usoskin, I.
Bibcode: 2008AGUSMGP31C..05U
Altcode:
Using a reconstruction of sunspot numbers stretching over multiple
millennia, we analyze the statistics of the occurrence of grand minima
and maxima and set new observational constraints on long-term solar
and stellar dynamo models. We present an updated reconstruction of
sunspot number over multiple millennia, from 14C data by means of
a physics-based model, using an updated model of the evolution of
the solar open magnetic flux. A list of grand minima and maxima of
solar activity is presented for the Holocene (since 9500 BC) and
the statistics of both the length of individual events as well as
the waiting time between them are analyzed. The occurrence of grand
minima/maxima appears to be driven not by long-term cyclic variability,
but by a stochastic/chaotic process. The waiting time distribution
of the occurrence of grand minima/maxima deviates from an exponential
distribution, implying that these events tend to cluster together with
long event-free periods between the clusters. Two different types
of grand minima are observed: short (30-90 years) minima of Maunder
type and long (>110 years) minima of Spörer type, implying that a
deterministic behaviour of the dynamo during a grand minimum defines
its length. The duration of grand maxima follows an exponential
distribution, suggesting that the duration of a grand maximum is
determined by a random process.
Title: Does sunspot number calibration by the "magnetic needle"
make sense?
Authors: Mursula, K.; Usoskin, I.; Yakovchouk, O.
Bibcode: 2008AGUSMSP23A..06M
Altcode:
It has been suggested recently that early sunspot numbers should be
re-calibrated and significantly corrected using the observed daily
range of the geomagnetic inclination (so called rY values). The
suggested "correction" method makes an a priori detrending of the rY
series and then extends the linear regression between rY and sunspot
numbers established for the last 25 years to earlier times. The
suggested "correction" of sunspot numbers by roughly 30% goes far
beyond the traditional estimates of observational uncertainties
of sunspots. Concentrating here on international sunspot numbers
(Rz), we demonstrate that the rY values do not actually imply
that the observed Rz values in the 19th century are systematically
underestimated. Rather, we find that the Rz numbers are fairly uniform
after mid-19th century. The suggested "correction" is largely induced
by the detrending of the rY series, which enhances the rY-based sunspot
activity in the 19th century relative to later times. We also show
that while the annually averaged declinations have a rough relation
between sunspots and other related solar parameters, this relation
is strongly seasonally dependent and nonlinear and, therefore, not
sufficiently accurate or uniform for rY to be used as a very reliable
proxy of solar activity in early times.
Title: Role of centennial geomagnetic changes in local atmospheric
ionization
Authors: Usoskin, I. G.; Korte, M.; Kovaltsov, G. A.
Bibcode: 2008GeoRL..35.5811U
Altcode:
Many studies of solar-terrestrial relation are based on globally (or
hemispherically) averaged quantities, including the average cosmic ray
flux. However, regional effects of cosmic ray induced ionization due to
geomagnetic changes may be comparable to or even dominate over the solar
signal at mid-latitudes on centennial-to-millennial time scales. We show
that local changes of the tropospheric ionization due to fast migration
of the geomagnetic axis are crucial on centennial time scale, and the
use of global averages may smear an important effect. We conclude that
changes of the regional tropospheric ionization at mid-latitudes are
defined by both geomagnetic changes and solar activity, and none of the
two processes can be neglected. This substantiates a necessity for a
careful analysis of the regional, not global, indices at mid-latitudes
and offers a new possibility to disentangle direct (solar radiation) and
indirect (via cosmic rays) effects in the solar-terrestrial relations.
Title: Cosmic Ray Induced Ion Production in the Atmosphere
Authors: Bazilevskaya, G. A.; Usoskin, I. G.; Flückiger, E. O.;
Harrison, R. G.; Desorgher, L.; Bütikofer, R.; Krainev, M. B.;
Makhmutov, V. S.; Stozhkov, Y. I.; Svirzhevskaya, A. K.; Svirzhevsky,
N. S.; Kovaltsov, G. A.
Bibcode: 2008pae..book..149B
Altcode:
An overview is presented of basic results and recent developments
in the field of cosmic ray induced ionisation in the atmosphere,
including a general introduction to the mechanism of cosmic ray
induced ion production. We summarize the results of direct and indirect
measurements of the atmospheric ionisation with special emphasis to
long-term variations. Models describing the ion production in the
atmosphere are also overviewed together with detailed results of
the full Monte-Carlo simulation of a cosmic ray induced atmospheric
cascade. Finally, conclusions are drawn on the present state and further
perspectives of measuring and modeling cosmic ray induced ionisation
in the terrestrial atmosphere.
Title: Forbush decreases: Energy dependence of the recovery
Authors: Usoskin, Ilya G.; Kovaltsov, Gennady A.; Gladysheva, Olga G.;
Jämsén, Teppo
Bibcode: 2008ICRC....1..327U
Altcode: 2008ICRC...30a.327U
We presented a statistical study of major Forbush decreases during
the last decades, using cosmic ray data from ground based detectors
-- neutron monitors and a muon detector. We show that, in addition to
typical event (e.g., September 2005), there are several unusual Forbush
decreases (e.g., November 2004), which depict unexpected features:
(1) the recovery time of a Forbush decrease strongly depends on the
mean response energy of the detector; (2) an over-recovery is observed
in the most energetic cosmic ray data (muon detector). Such a behavior
is not expected from the standard theory of a Forbush decrease. Here
we suggest a simple qualitative scenario for the observed phenomenon.
Title: Numerical Model of Cosmic Ray Induced Ionization in the
Atmosphere
Authors: Usoskin, Ilya G.; Kovaltsov, Gennady A.
Bibcode: 2008ICRC....1..705U
Altcode: 2008ICRC...30a.705U
We present a physical model to calculate cosmic ray induced ionization
in the atmosphere. The model is based on the Monte-Carlo CORSIKA tool,
which simulates full development of an electromagnetic-muon-nucleonic
cascade in the atmosphere, with the FLUKA package used for low energy
interactions. The model is applicable to the entire atmosphere,
from the ground up to the stratosphere. A comparison to fragmentary
direct measurements of the ionization in the atmosphere confirms the
validity of the model in the whole range of geographical latitudes and
altitudes. We provide a detailed recipe to compute easily the cosmic
ray induced ionization for given location, altitude and the spectrum of
cosmic rays. This provides a new tool for a quantitative study of the
space weather influence upon the Earth's environment. Some practical
applications are discussed.
Title: Rapid cosmic ray fluctuations in real-time during the SEP
events in December 2006
Authors: Starodubtsev, S. A.; Grigoryev, A. V.; Usoskin, I. G.;
Mursula, K.
Bibcode: 2008ICRC....1..135S
Altcode: 2008ICRC...30a.135S
Cosmic ray fluctuations with the periods less than 3 h by data
of the EPAM/LEMS120 aboard ACE spacecraft are studied. It is shown
that the frequency spectra of cosmic rays undergo significant dynamic
changes caused by the presence of fast magnetosonic waves in the solar
wind. Evidences of generation of fast magnetosonic waves by the SEP
fluxes have been found.
Title: Grand minima and maxima of solar activity on multi-millennial
scale
Authors: Usoskin, Ilya; Solanki, Sami; Kovaltsov, Gennady
Bibcode: 2008cosp...37.3264U
Altcode: 2008cosp.meet.3264U
Using a reconstruction of sunspot numbers stretching over multiple
millennia, we analyze the statistics of the occurrence of grand minima
and maxima and set new observational constraints on long-term solar
and stellar dynamo models. We present an updated reconstruction of
sunspot number over multiple millennia, from 14C data by means of
a physics-based model, using an updated model of the evolution of
the solar open magnetic flux. A list of grand minima and maxima of
solar activity is presented for the Holocene (since 9500 BC) and
the statistics of both the length of individual events as well as
the waiting time between them are analyzed. It is discussed that the
occurrence of grand minima/maxima is driven not by long-term cyclic
variability, but by a stochastic/chaotic process. The waiting time
distribution of the occurrence of grand minima/maxima deviates from an
exponential distribution, implying that these events tend to cluster
together with long event-free periods between the clusters. Two
different types of grand minima are observed: short (30-90 years)
minima of Maunder type and long (>110 years) minima of Sp¨rer type,
implying that a deterministic behaviour of the dynamo during o a grand
minimum defines its length. The duration of grand maxima follows an
exponential distribution, suggesting that the duration of a grand
maximum is determined by a random process.
Title: Fluctuations of cosmic rays and IMF in the vicinity of
interplanetary shocks
Authors: Grigoryev, A. V.; Starodubtsev, S. A.; Grigoryev, V. G.;
Usoskin, I. G.; Mursula, K.
Bibcode: 2008AdSpR..41..955G
Altcode:
Fluctuations of cosmic rays and interplanetary magnetic field upstream
of interplanetary shocks are studied using data of ground-based polar
neutron monitors as well as measurements of energetic particles and
solar wind plasma parameters aboard the ACE spacecraft. It is shown
that coherent cosmic ray fluctuations in the energy range from 10 keV
to 1 GeV are often observed at the Earth’s orbit before the arrival
of interplanetary shocks. This corresponds to an increase of solar
wind turbulence level by more than the order of magnitude upstream
of the shock. We suggest a scenario where the cosmic ray fluctuation
spectrum is modulated by fast magnetosonic waves generated by flux of
low-energy cosmic rays which are reflected and/or accelerated by an
interplanetary shock.
Title: Stochastic simulation of cosmic ray modulation: Effect of a
wavy HCS
Authors: Usoskin, Ilya G.; Alanko-Huotari, Katja; Mursula, Kalevi;
Kovaltsov, Gennady A.
Bibcode: 2008ICRC....1..459U
Altcode: 2008ICRC...30a.459U
We present a new method to include a wavy heliospheric current sheet
into a 2D numerical model of the heliospheric transport of galactic
cosmic rays. Since the wavy current sheet has essentially 3D structure,
we have developed an approach of averaging the corresponding drift
effect over all longitudes for an axisymmetric model. First, an
analytical solution is found for the flat sheet, this model then is
applied to a wavy sheet assuming its local quasi-flatness. We study
cosmic ray modulation in different solar modulation conditions and
waviness of the current sheet. We discuss changes in the cosmic ray
spectrum and the dominant streaming patterns of cosmic rays in the
heliosphere for different solar polarities and HCS tilt angles.
Title: Role of centennial geomagnetic changes in local atmospheric
ionization
Authors: Usoskin, Ilya; Korte, Monika; Kovaltsov, Gennady
Bibcode: 2008cosp...37.3266U
Altcode: 2008cosp.meet.3266U
Many studies of solar-terrestrial relation are based on globally (or
hemispherically) averaged quantities, including the average cosmic ray
flux. However, regional effects of cosmic ray induced ionization due to
geomagnetic changes may be comparable to or even dominate over the solar
signal at mid-latitudes on centennial-to-millennial time scales. We show
that local changes of the tropospheric ionization due to fast migration
of the geomagnetic axis are crucial on centennial time scale, and the
use of global averages may smear an important effect. We conclude that
changes of the regional tropospheric ionization at midlatitudes are
defined by both geomagnetic changes and solar activity, and none of the
two processes can be neglected. This substantiates a necessity for a
careful analysis of the regional, not global, indices at mid-latitudes
and offers a new possibility to disentangle direct (solar radiation) and
indirect (via cosmic rays) effects in the solar-terrestrial relations.
Title: Forbush decreases of cosmic rays: Does the recovery phase
depend on energy?
Authors: Usoskin, Ilya; Braun, Isabel; Gladysheva, Olga; Hoerandel,
J. R.; Kovaltsov, Gennady; Jamsen, Teppo; Starodubtsev, Sergei
Bibcode: 2008cosp...37.3265U
Altcode: 2008cosp.meet.3265U
While the cause and general shape of Forbush decreases of cosmic ray
intesnity are relatively well understood, physical modelling of their
recovery still remains rather poor. Earlier results of theoretical
and fragmentary statistical studies are inconsistent in the sense
whether the recovery time depends on the energy of cosmic rays. A
thorough empirical study of the recovery phase of strong isolated
Forbush decreases is presented here, based on the ground based data
from the World Neutron Monitor Network since 1964 and three ground
based muon telescopes since 1973. We have analyzed a total of 39 strong
Forbush decreases. About 60% of them (24) of them depict a clear energy
dependence of the recovery time and 15 are consistent with no energy
dependence. The recovery rate depicts a strong energy dependence for all
analyzed strong Forbush decreases, with a magnitude exceeding 10%, while
smaller events can be of either type. We found no apparent relation
between the occurrence of energy dependent/independent recovery and
the IMF polarity. This result provides an observational constraint for
more detailed modeling of the propagation of interplanetary transients
and their dynamic effects on cosmic ray transport.
Title: Grand Minima of solar activity : Random fluctuations in
dynamo parameters
Authors: Usoskin, Ilya; Moss, David; Sokoloff, Dmitry
Bibcode: 2008cosp...37.3267U
Altcode: 2008cosp.meet.3267U
A recent statistical study of the rate and regularity of Grand Minima
occurrence on a multimillennial time scale poses new observational
constraints on solar dynamo theory. We consider to what extent the
long-term dynamics of cyclic solar activity in the form of Grand Minima
can be associated with random fluctuations of the parameters governing
the solar dynamo. We consider fluctuations of the alpha-coefficient in
the conventional Parker migratory dynamo, and also in slightly more
sophisticated dynamo models, and demonstrate that they can mimic the
principal features of the phenomenon of the occurrence of Grand Minima
over a suitable parameter range. The temporal distribution of these
Grand Minima appears chaotic, with a more or less exponential waiting
time distribution, typical of Poisson processes. In contrast however,
the available reconstruction of Grand Minima statistics based on
cosmogenic isotope data demonstrates substantial deviations from this
exponential law. We were unable to reproduce the non-Poissonic tail
of the waiting time distribution either in the framework of a simple
alpha-quenched Parker model, or in its straightforward generalization,
nor in simple models with feedback on the differential rotation. We
suggest that the disagreement may only be apparent and is plausibly
related to the limited observational data, and that the observations
and results of numerical modeling can be consistent and represent
physically similar dynamo regimes.
Title: Stochastic simulation of cosmic ray modulation including a
wavy heliospheric current sheet
Authors: Alanko-Huotari, K.; Usoskin, I. G.; Mursula, K.; Kovaltsov,
G. A.
Bibcode: 2007JGRA..112.8101A
Altcode: 2007JGRA..11208101A
We present a quasi-steady two-dimensional (axisymmetric) model of the
heliospheric transport of galactic cosmic rays. The model is based
on stochastic simulation techniques and includes all the modulation
mechanisms that cosmic rays experience in the heliosphere: convection,
adiabatic cooling, diffusion, and drifts. A special emphasis is
given to the cosmic ray transport in the vicinity of the heliospheric
current sheet (HCS), and a new method to calculate the wavy current
sheet drift is presented. We study cosmic ray modulation in different
solar modulation conditions and levels of waviness of the current
sheet. We discuss changes in the cosmic ray spectrum and the dominant
streaming patterns of cosmic rays in the heliosphere for different
solar polarities and HCS tilt angles.
Title: Grand minima and maxima of solar activity: new observational
constraints
Authors: Usoskin, I. G.; Solanki, S. K.; Kovaltsov, G. A.
Bibcode: 2007A&A...471..301U
Altcode: 2007arXiv0706.0385U
Aims:Using a reconstruction of sunspot numbers stretching over
multiple millennia, we analyze the statistics of the occurrence of
grand minima and maxima and set new observational constraints on
long-term solar and stellar dynamo models.
Methods: We present
an updated reconstruction of sunspot number over multiple millennia,
from 14C data by means of a physics-based model, using an
updated model of the evolution of the solar open magnetic flux. A
list of grand minima and maxima of solar activity is presented for
the Holocene (since 9500 BC) and the statistics of both the length
of individual events as well as the waiting time between them are
analyzed.
Results: The occurrence of grand minima/maxima is
driven not by long-term cyclic variability, but by a stochastic/chaotic
process. The waiting time distribution of the occurrence of grand
minima/maxima deviates from an exponential distribution, implying that
these events tend to cluster together with long event-free periods
between the clusters. Two different types of grand minima are observed:
short (30-90 years) minima of Maunder type and long (>110 years)
minima of Spörer type, implying that a deterministic behaviour of
the dynamo during a grand minimum defines its length. The duration of
grand maxima follows an exponential distribution, suggesting that the
duration of a grand maximum is determined by a random process.
Conclusions: These results set new observational constraints upon
the long-term behaviour of the solar dynamo.
Title: (1) Preferred longitudes in sunspot activity (2) Preferred
sunspot longitudes: non-axisymmetry and differential rotation
Authors: Usoskin, I. G.; Berdyugina, S. V.; Poutanen, J.
Bibcode: 2007A&A...464..761U
Altcode:
No abstract at ADS
Title: Cyclic variations of the heliospheric tilt angle and cosmic
ray modulation
Authors: Alanko-Huotari, K.; Usoskin, I. G.; Mursula, K.; Kovaltsov,
G. A.
Bibcode: 2007AdSpR..40.1064A
Altcode:
Using data on cosmic ray modulation parameter since 1951, we have
estimated the evolution of the heliospheric current sheet tilt angle
for the period 1951-1975, i.e., 25 years before regular observations of
the tilt angle. This estimate is based on our recent empirical model
relating cosmic ray intensity with global heliospheric parameters. We
propose a simple model to describe the cyclic evolution of the
tilt angle with the solar cycle. This model agrees with available
observational data. Using this model, we have estimated the cosmic
ray intensity since 1710. This estimate is consistent with the results
based on cosmogenic isotopes ( 14C and 10Be).
Title: Long-term persistence of solar active longitudes and its
implications for the solar dynamo theory
Authors: Usoskin, I. G.; Berdyugina, S. V.; Moss, D.; Sokoloff, D. D.
Bibcode: 2007AdSpR..40..951U
Altcode:
We present an overview of the observational results related to the
existence of long-lived sunspot active longitudes. These are affected
by the solar differential rotation. The existence of such migrating
active longitudes imposes an important constraint on the dynamo
theory. We review different approaches to model non-axisymmetry in
solar dynamo models and find that, in principle, plausible mechanisms
exist to reproduce the observed non-axisymmetry. The most favorable
interpretation is suggested by the 'stroboscopic effect', where
a quasi-rigidly rotating non-axisymmetric mean field can produce
seemingly migrating active longitudes in sunspots. Other scenarios
are less favorable but cannot yet be excluded.
Title: Effect of ENSO and volcanic events on the Sun cloud link
Authors: Voiculescu, Mirela; Usoskin, Ilya; Mursula, Kalevi
Bibcode: 2007AdSpR..40.1140V
Altcode:
Results of correlation studies between solar proxies and clouds suggest
that there is a solar effect on the occurrence of clouds. However, there
is a possibility that terrestrial quasi-periodic and sporadic phenomena,
such as ENSO and/or major volcanic eruptions, which have an effect on
the cloud formation, may influence the results of statistical studies of
the Sun-cloud relation. We show that removing ENSO and volcanic years
from the full-set analysis does not alter the results. Moreover, the
correlation between clouds of different type and two solar proxies, UV
irradiance and cosmic ray induced ionisation, is partly improved. This
supports the idea that the solar signal affects clouds directly. An
interesting result relates to an area in the eastern Pacific where
the full-set analysis showed that the relationship between clouds
and cosmic ray induced ionization is opposite to the global one. When
ENSO and volcanic years are removed this odd correlation disappears,
suggesting that in this particular area, the ENSO effect prevails over
solar effects.
Title: Case study of Forbush decreases: Energy dependence of the
recovery
Authors: Jämsén, T.; Usoskin, I. G.; Räihä, T.; Sarkamo, J.;
Kovaltsov, G. A.
Bibcode: 2007AdSpR..40..342J
Altcode:
Case study is presented for three Forbush decreases in 2004-2005,
using cosmic ray data from ground-based detectors - neutron monitors
and a muon detector. One of them was a typical event (September 2005),
while two other were quite unusual (November 2004 and January 2005). Two
unusual features, not expected from the standard theory, are revealed:
(1) the recovery time of a Forbush decrease can strongly depend on
the energy; (2) an over-recovery is observed in the most energetic
cosmic ray data (muon detector). A simple scenario is suggested for
the observed phenomenon.
Title: Introduction to Space Climate
Authors: Mursula, K.; Usoskin, I. G.; Maris, G.
Bibcode: 2007AdSpR..40..885M
Altcode:
"Space Climate" is a relatively new scientific concept, which combines
a number of disciplines in space and atmospheric sciences under the
common aim to better understand the long-term changes in the Sun,
heliosphere and in the near-Earth environment. In this brief summary
we define the contents and aims of Space Climate. We also review some
recent findings that are discussed in the papers included in this issue
of Advances in Space Research, noting on some problems that should
be solved, as well as some new lines of research that could lead to
a better understanding of some of the main questions of Space Climate.
Title: Correlation between clouds at different altitudes and solar
activity: Fact or Artifact?
Authors: Usoskin, I. G.; Voiculescu, M.; Kovaltsov, G. A.; Mursula, K.
Bibcode: 2006JASTP..68.2164U
Altcode: 2006JATP...68.2164U
Studies of the relation between cosmic rays (CR) (solar activity) and
atmospheric cloudiness are mostly based on the satellite ISCCP cloud
data. However, doubts have been cast that these relations can be an
artifact of instrumental effects, i.e., of the masking/obscuring low
clouds by higher clouds in the satellite view. If this is the case, most
of the earlier results based on ISCCP data would be devaluated. Here,
we reanalyze the ISCCP cloud coverage data and its relation with the
cosmic ray-induced ionization, and show that the correlation between
low clouds and CR is affected by higher clouds in some geographical
regions, but not everywhere. In turn, our results show that low
clouds also may affect the relation of higher clouds with CR in some
regions. Accordingly, correlation analysis can be performed only
when the strong relation between clouds of different types is taken
into account. In particular, studies based on global or latitudinal
(zonally averaged) cloud data should be revised.
Title: On possible drivers of Sun-induced climate changes
Authors: de Jager, Cornelis; Usoskin, Ilya
Bibcode: 2006JASTP..68.2053D
Altcode: 2006JATP...68.2053D
We tested the validity of two current hypotheses on the dependence of
climate change on solar activity. One of them states that variations in
the tropospheric temperature are caused directly by changes of the solar
radiance (total or spectral). The other suggests that cosmic ray (CR)
fluctuations, caused by the solar/heliospheric modulation, affect the
climate via cloud formation. Confronting these hypotheses with seven
different sets of the global/hemispheric temperature reconstructions
for the last 400 years, we found that the former mechanism is in
general more prominent than the latter. Therefore, we can conclude
that in so far as the Sun climate connection is concerned tropospheric
temperatures are more likely affected by variations in the UV radiation
flux rather than by those in the CR flux.
Title: Global Heliospheric Parameters and Cosmic-Ray Modulation:
An Empirical Relation for the Last Decades
Authors: Alanko-Huotari, K.; Mursula, K.; Usoskin, I. G.; Kovaltsov,
G. A.
Bibcode: 2006SoPh..238..391A
Altcode: 2006SoPh..tmp...83A
We study empirical relations between the modulation of galactic
cosmic rays quantified in terms of the modulation potential and the
following global heliospheric parameters: the open solar magnetic flux,
the tilt angle of the heliospheric current sheet, and the polarity of
the heliospheric magnetic field. We show that a combination of these
parameters explains the majority of the modulation potential variations
during the neutron monitor era 1951 - 2005. Two empirical models
are discussed: a quasi-linear model and a model assuming a power-law
relation between the modulation potential and the magnetic flux. Both
models describe the data fairly well. These empirical models provide
a simple tool for evaluating various cosmic-ray related effects on
different time scales. The models can be extended backwards in time
or used for predictions, if the corresponding global heliospheric
variables can be independently estimated.
Title: Different response of clouds to solar input
Authors: Voiculescu, Mirela; Usoskin, Ilya G.; Mursula, Kalevi
Bibcode: 2006GeoRL..3321802V
Altcode:
There is evidence that solar activity variations can affect the cloud
cover at Earth. However, it is still unclear which solar driver plays
the most important role in the cloud formation. Here we use partial
correlations to distinguish between the effects of two solar drivers
(cosmic rays and the UV irradiance) and the mutual relations between
clouds at different altitudes. We find that the solar influence on
cloud cover is not uniquely defined by one solar driver, but both seem
to play a role depending on the climatic conditions and altitude. In
particular, low clouds are mostly affected by UV irradiance over oceans
and dry continental areas and by cosmic rays over some mid-high latitude
oceanic areas and moist lands with high aerosol concentration. High
clouds respond more strongly to cosmic ray variations, especially over
oceans and moist continental areas. These results provide observational
constraints on related climate models.
Title: Long-term solar activity reconstructions: direct test by
cosmogenic 44Ti in meteorites
Authors: Usoskin, I. G.; Solanki, S. K.; Taricco, C.; Bhandari, N.;
Kovaltsov, G. A.
Bibcode: 2006A&A...457L..25U
Altcode:
Aims.Long-term solar activity in the past is usually estimated from
cosmogenic isotopes, 10Be or 14C, deposited in
terrestrial archives such as ice cores and tree rings. A number of such
reconstruction models have been proposed which differ from each other
significantly. This approach suffers, however, from uncertainties due
to the sensitivity of the data to several terrestrial processes. Here
we propose a method to constrain these solar activity reconstructions
using cosmogenic 44Ti activity in meteorites which is
not affected by terrestrial processes.
Methods: .We test the
veracity of recent solar activity reconstructions using the data on
the activity of cosmogenic isotope 44Ti in meteorites which
fell during the past 235 years, and provide an independent and direct
measure of the cosmic ray flux near the Earth and allow decoupling of
solar activity variations from terrestrial influences.
Results:
.We demonstrate that the 44Ti data can distinguish between
various reconstructions of past solar activity based on cosmogenic
isotope data in terrestrial archives, allowing unrealistic models to
be ruled out. We also show that a model based on the sunspot number
record is consistent with the data on 44Ti activity in
meteorites, thus confirming the validity of the method. In particular
the 44Ti data confirm significant secular variations of
the solar magnetic flux during the last century.
Title: An upper limit of sunspot activity during the Maunder minimum
Authors: Usoskin, I. G.; Kovaltsov, G. A.; Mursula, K.
Bibcode: 2006IAUJD...8E..15U
Altcode:
The Maunder minimum (1645-1715) is of great interest for solar activity
studies. During that period, sunspot activity was at the very low level,
indicating a specific state of the solar dynamo corresponding to a
grand minimum. However, the exact level of sunspot activity during
the Maunder minimum is still debated. The Maunder minimum period was
amazingly well covered by sunspot data, but some of these data are
based not on direct daily drawings/ counts of sunspots but on general
statements on the absence of spots during long periods. Although such
statements were done by highly qualified astronomers, this fact has led
to speculations that the actual sunspot activity level in the earlier
part of the Maunder minimum could have been higher than suggested in the
group sunspot number series. Here we have estimated conservative upper
and lower limits of sunspot activity as obtained from direct sunspot
observation records. We use the concept of active day fraction during
the Maunder minimum, applied to the raw information on individual daily
observations. Establishing the relation between the sunspot activity
and active day fraction after 1850, we have evaluated the upper limit of
annual group sunspot number during the deep Maunder minimum (1645-1700)
which does not exceed 4. The solar cycle in 1700-1710 has been shown to
be tiny, below 8 in sunspot numbers. The earlier finding of a dominant
22-year periodicity during the Maunder minimum is confirmed as well
as the abrupt start of the minimum.
Title: The modern high solar activity: How unusual is it?
Authors: Usoskin, I. G.
Bibcode: 2006IAUJD...8E..14U
Altcode:
The history of direct solar observations is 400-years long, but for
many purposes longer series are needed. On the longer time scales,
indirect proxy data like cosmogenic nuclides should be used to evaluate
the past level of solar activity. Here I present a reconstruction
of the solar activity on the multi-millennial time scale using
physics-based models for the whole chain of processes between the Sun
and Earth. The reconstructed activity depicts great variability, from
grand minima with almost vanishing sunspot activity to grand maxima,
when the activity was comparable to the contemporary high activity
level. The fraction of time that the Sun spends in grand minima and
hyper-active states is evaluated. In particular, these reconstructions
imply that the contemporary high level of solar activity is quite
exceptional on the multi-millennial time scale. Possible uncertainties
of reconstructions are discussed in details, including random errors
as well as systematic uncertainties, related, e.g., to the geomagnetic
field model. The conclusion about the unusually high contemporary level
of solar activity on the multi-millennial time scale is confirmed
to be robust by using different methods. Implications for the solar
dynamo and solar-terrestrial connections are discussed as well.
Title: Solar proton events in cosmogenic isotope data
Authors: Usoskin, Ilya G.; Solanki, Sami K.; Kovaltsov, Gennady A.;
Beer, Jürg; Kromer, Bernd
Bibcode: 2006GeoRL..33.8107U
Altcode:
A possible contribution of solar energetic particle events to the
production of cosmogenic 10Be and 14C in the
atmosphere is studied. The solar particle effect is negligible in
the 14C data, but extreme events may be detectable in
high-resolution 14C data. Although the overall effect
is small in the 10Be data, strong events may contribute
notably on the inter-annual time scale. In combination with the
11-year solar modulation of galactic cosmic rays, it may lead to an
intermittent 5.5-year periodicity, which is seen in high resolution
10Be data. We have identified ten episodes during 1750-1950
when 10Be may hold signatures of strong solar proton
events. This opens a new possibility to study extreme solar particle
events in the past using high resolution cosmogenic isotope data.
Title: Solar activity reconstructed over the last 7000 years: The
influence of geomagnetic field changes
Authors: Usoskin, I. G.; Solanki, S. K.; Korte, M.
Bibcode: 2006GeoRL..33.8103U
Altcode:
The long-term solar activity, as manifested by sunspot number,
has been recently reconstructed on multi-millennium time scales
by S. K. Solanki et al. (2004) from the measured concentration of
14C in tree rings. The exact level of the reconstructed
solar activity depends, however, on independently evaluated data of
the geomagnetic dipole strength variations. Recently, a new series
of the palaeomagnetic dipole moment reconstruction for the last 7000
years has been presented by M. Korte and C. G. Constable (2005a) on the
basis of a thorough analysis of global samples. The new palaeomagnetic
series yields a systematically lower dipole moment in the past,
compared to the earlier geomagnetic reconstructions. We have revised
the earlier sunspot activity reconstruction since 5000 BC, using the
new geomagnetic data series, and found that it is roughly consistent
with the previous results during most of the period, although the
revised sunspot number values are in general higher. Nonetheless, it
is confirmed with the new palaeomagnetic series that the Sun spends
only 2-3% of the time in a state of high activity, similar to the
modern episode. This strengthens the conclusion that the modern high
activity level is very unusual during the last 7000 years.
Title: Long-term modulation of the cosmic ray fluctuation spectrum
Authors: Starodubtsev, S. A.; Usoskin, I. G.; Grigoryev, A. V.;
Mursula, K.
Bibcode: 2006AnGeo..24..779S
Altcode:
Here we study the power level of rapid cosmic ray fluctuations
in the frequency range of 10-4-1.67·10-3 Hz
(periods from 10 min to about 3 h), using measurements by space-borne
instruments for the period since 1974. We find that the power level
of these fluctuations varies over the solar cycle, but the phase of
this variation depends on the energy of cosmic ray particles. While
the power level of these fluctuations in the higher energy channels
(corresponding to galactic cosmic rays) changes in phase with the solar
cycle, the fluctuation level for lower energy channels (predominantly of
solar/interplanetary origin) is roughly in an opposite phase with the
solar cycle. The results prove conclusively that these fluctuations
originate in the near-Earth space, excluding their atmospheric or
magnetospheric origin. We present these new results and discuss a
possible scenario explaining the observed energy-dependence.
Title: The Solar Cycle at the Maunder Minimum Epoch
Authors: Miyahara, Hiroko; Sokoloff, Dmitry; Usoskin, Ilya G.
Bibcode: 2006aogs....2....1M
Altcode:
Here, we present a brief review of the current status of the Maunder
minimum study. The Maunder minimum is considered as an example of
occasionally occurring Grand minima, when the solar dynamo was in a
special mode. We review available sets of direct and indirect data
covering the period during and around the Maunder minimum. The start
of the minimum was very abrupt and was followed by a gradual recovery
of the activity. The data suggest that while the sunspot activity was
greatly suppressed during the deep phase of the minimum, the cyclic
dynamo kept working around the sunspot formation threshold level,
leading to seemingly sporadic occurrence of sunspots. The majority of
proxy data depict the dominant 22-year periodicity during the Maunder
minimum with the sub-dominant 11-year cycle. The length of the cycles
was probably slightly enhanced. We also discuss theoretical models and
speculations concerning the solar dynamo as well as the heliosphere
during the Maunder minimum. Comparison with other minima (Spörer and
Dalton) suggests that these features are common.
Title: Multi-millennium changes of the geomagnetic field and solar
activity
Authors: Usoskin, I. G.; Solanki, S.; Korte, M.
Bibcode: 2006cosp...36.2281U
Altcode: 2006cosp.meet.2281U
The long-term solar activity has been recently reconstructed on
the multi-millennium time scale Solanki et al Nature 431 384 2004
from the measured concentration of radiocarbon 14 C in tree rings
The exact level of the reconstructed solar activity depends however
on independently evaluated data of the geomagnetic dipole strength
variations Recently a new series of the palaeomagnetic dipole moment
reconstruction for the last 7000 years has been presented by Korte and
Constable Earth Plan Sci Lett 236 348 2005 on the basis of a thorough
complex analysis of global samples The new palaeomagnetic series yields
systematically lower dipole moment in the past compared to the earlier
geomagnetic reconstructions We have revised the earlier sunspot activity
reconstruction since 5000 BC using the new geomagnetic data and found
that it is consistent with the previous results during most of the
period although it yields a slightly higher level of the reconstructed
sunspot activity The earlier finding on the very unusual level of the
contemporary solar activity over the last millennia is confirmed with
the new palaeomagnetic series The Sun spent only 2-3 of the time in
a high activity state similar to the modern episode implying that the
modern high activity level is very unusual during the last 7000 years On
the other hand grand minima occupy about 12 of the time in the recent
history of the Sun The new reconstruction allows for a comparative
study of solar-terrestrial relations in the multi-millennium time scale
Title: Cosmic ray induced ionization in the atmosphere: An improved
model
Authors: Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2006cosp...36.2293U
Altcode: 2006cosp.meet.2293U
We present a full quantitative physical model to calculate cosmic
ray induced ionization in the atmosphere The model is based on the
Monte-Carlo CORSIKA tool which simulates the full development of an
electromagnetic-muon-nucleonic cascade in the atmosphere with the FLUKA
package used for low energy interactions The model is applicable to the
entire atmosphere from the ground up to the stratosphere A comparison
to direct measurements of the ionization in the atmosphere confirms
the validity of the model in the whole range of geographical latitudes
and altitudes This provides a new tool for a quantitative study of the
space weather influence upon the Earth s environment We apply the model
to study the cosmic ray induced ionization on different time scales
In particular variations of the induced ionization are calculated for
the last centuries and show a great variability about 50 between the
modern period and the Maunder minimum
Title: Empirical relations between the cosmic ray flux and the
heliospheric current sheet tilt angle
Authors: Alanko-Huotari, K.; Usoskin, I. G.; Mursula, K.
Bibcode: 2006cosp...36.1972A
Altcode: 2006cosp.meet.1972A
One of the main factors in the heliospheric modulation of galactic
cosmic rays is the tilt angle of the heliospheric current sheet which
is formed as an interface between the oppositely directed field lines
of the HMF and corresponds to the heliomagnetic equator The structure
of the current sheet is defined by the tilt angle between the magnetic
and rotational axes of the Sun which depends on the phase of the
solar cycle Due to the charge-dependent drift of cosmic rays along
the current sheet variations of the tilt angle in the course of the
solar cycle results in a notable variation of cosmic ray flux in the
Earth s vicinity An empirical model relating the cosmic ray flux with
such global heliospheric parameters as the tilt angle the open solar
flux and the polarity of the heliospheric magnetic field was developed
Inverting this model we study a possibility to evaluate the tilt angle
in the past before its measurements Comparing the model results with
the actual measurements of the tilt angle which have been carried out
for the last 30 years we confirm the validity of the method Finally we
extend our model to cover the last 55 years providing thus an estimate
of the tilt angle for nearly 20 years before the actual measurements
Title: Evidence for the generation of MHD- turbulence by energetic
storm particles
Authors: Starodubtsev, S. A.; Grigoryev, A. V.; Usoskin, I. G.;
Mursula, K.
Bibcode: 2006cosp...36.1862S
Altcode: 2006cosp.meet.1862S
Here we present a study of the MHD-turbulence generation in the IMF
fluctuation spectrum observed in the pre-shock front region of an
interplanetary shock We have studied 177 interplanetary shocks recorded
aboard the ACE spacecraft between 1998 and 2003 As a result we have
found 19 shock events when the energy density was essentially increased
just before the front by orders of magnitude from 10 -12 to 10 -10 ergs
cm 3 in the frequency range of 10 -4 - 3 125 10 -2 Hz i e sometimes it
is comparable to that of the undisturbed large-scale IMF Thereby the
field and plasma parameters remain undisturbed while considerable fluxes
of energetic storm particles are observed We conclude that generation
of MHD-waves and a subsequent increase of the level of small-scale
turbulence in the pre-front range are caused by these storm particles
Title: Link Between Cosmic Rays and Clouds on Different Time Scales
Authors: Usoskin, Ilya G.; Kovaltsov, Gennady A.
Bibcode: 2006aogs....2..321U
Altcode:
A possible mechanism of solar variability influence upon the
Earth's climate is related to a link between the cosmic ray flux and
cloudiness. Here we review evidences relating terrestrial climate
variability to changes of cosmic ray flux in the Earth's vicinity on
different time scales. On daily scales, major For-bush decreases and
solar energetic particle events can affect the cyclogenesis in sub-polar
regions. At inter-annual scales, a significant correlation between low
clouds and cosmic ray induced ionization has been found. Different
climate reconstructions depict a correlation with variations of the
geomagnetic field intensity throughout the last millennia, providing
additional support to a systematic effect of cosmic rays. On very
long time scales, a close relation was reported between the global
climate and variations of cosmic ray flux expected from local galactic
environment changes. Although none of these facts alone is conclusive,
in the aggregate they strongly support the link between cosmic rays and
climate on Earth. These links are based on phenomenological relations,
and theoretical development and experimental investigation of this
hypothesis is ongoing.
Title: Link between solar activity and cloud cover: Fact or artifact?
Authors: Voculescu, M.; Usoskin, I. G.; Kovaltsov, G. A.; Mursula, K.
Bibcode: 2006cosp...36.2291V
Altcode: 2006cosp.meet.2291V
While it is commonly accepted that the solar activity affects the
Earth climate the exact driving process is still not identified An
important potential driver is a link between cosmic rays and cloud
cover suggested on the basis of extensive correlation studies of cosmic
rays solar activity and atmospheric cloudiness Such studies are mostly
based on the satellite ISCCP cloud data However doubts have been cast
that these relations can be an artifact of instrumental effects i e of
the masking obscuring the low clouds by higher clouds in the satellite
view If this is the case most of the earlier results based on ISCCP data
would be devaluated Here we re-analyze the ISCCP cloud coverage data and
its relation with the cosmic ray induced ionization and show that the
correlation between low clouds and cosmic rays is affected by higher
clouds in some geographical regions but it is not a global feature In
turn our results show that low clouds also may affect the relation of
higher clouds with cosmic rays in some regions Accordingly correlation
analysis can be performed only when the strong relation between clouds
of different types is taken into account In particular studies based
on global or latitudinal zonally averaged cloud data should be revised
Title: What do we know about the link between cosmic rays and climate?
Authors: Usoskin, I. G.
Bibcode: 2006cosp...36.2287U
Altcode: 2006cosp.meet.2287U
Although there is a general agreement that the solar activity affects
the Earth s climate details are still missing One of the potential
mechanisms of the solar variability influence upon the Earth s climate
is via the cosmic ray flux bombarding the Earth s atmosphere that can
affect the cloud formation Here we review different pieces of evidence
relating the terrestrial climate variability to changes of cosmic
ray flux in the Earth s vicinity on different time scales On daily
scales there are hints on the instantaneous relation between short term
variations of cosmic rays and either the cloud amount vorticity indices
At inter-annual scales impressing correlation between low clouds and
cosmic ray induced ionization has been found but it appears significant
only in some geographical areas Although a link between solar activity
and climate seems plausible on millennial time scale only a marginal
correlation between palaeoclimatic data and geomagnetic field variations
supports the idea of cosmic ray influence On very long time scales a
close relation was reported between the global climate and variations of
cosmic ray flux expected from changes in the local galactic environment
However large uncertainties make this result only indicative Although
none of these facts alone is conclusive in the aggregate they support
the link between cosmic rays and the Earth s climate These results
are based on phenomenological relations and theoretical development
and experimental investigation of this hypothesis is ongoing
Title: Variations of cosmic ray flux: From decades to millennia
Authors: Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2006cosp...36.2282U
Altcode: 2006cosp.meet.2282U
Galactic cosmic rays are subject to modulation in the heliosphere
because of different processes e g diffusion convection and adiabatic
deceleration in solar wind with frozen-in magnetic field as well as
charge-dependent drift effects While sophisticated theoretical models
have been developed corresponding to advanced understanding of the
modulation process they can be hardly applied to the past when only very
limited and mostly indirect information exists on the solar heliospheric
parameters In this case special efforts should be taken to study the
modulation We apply such methods based on reasonable simplification
and coarsening of full models to the study of heliospheric modulation
at different time scales and discuss the main heliospheric parameters
of the cosmic ray modulation We present some results of the long-term
modulation study covering the time scales from a solar cycle to the
millennial scale
Title: Fluctuations of cosmic rays and IMF in the vicinity of an
interplanetary shock
Authors: Starodubtsev, S. A.; Grigoryev, A. V.; Usoskin, I. G.;
Mursula, K.
Bibcode: 2006cosp...36..902S
Altcode: 2006cosp.meet..902S
Fluctuations of IMF and cosmic rays in the pre-front region of
interplanetary shocks are studied using direct measurements of the solar
wind parameters and cosmic ray intensity onboard the ACE spacecraft as
well as cosmic rays at ground based polar stations It is shown that
coherent fluctuations of cosmic ray flux in the energy range between
100 keV and 1 GeV are observed during energetic storm particles ESP
events This is typically accompanied by an increase of the level of
the solar wind turbulence by an order of magnitude on the average We
conclude that the cosmic ray fluctuation spectrum is modulated by fast
magnetosonic waves generated by strong fluxes of ESP in the pre-front
region of an interplanetary shock
Title: Establishing a Cosmic Ray Station and Other Space Research
Facilities in Ethiopia
Authors: Damtie, B.; Bosinger, T.; Usoskin, I.
Bibcode: 2006AfrSk..10...29D
Altcode:
This paper describes the potential of Ethiopia in establishing
space research facilities and conducting collaborative research and
training. It also describes the goals and objectives of a proposed
cosmic ray station in Ethiopia which would greatly improve the
abilities of the existing worldwide network for heliospheric and
cosmic ray research. The station will be located at the geomagentic
equator, which is a very unique place for geomagnetic and heliospheric
studies. Moreover, the paper presents an overview of the research and
training activities in space physics and the successful collaborative
project between Ethiopia and Finland, which facilitated the installation
of a pulsation magnetometer and a photometer at Entoto Mountain in a
suburb of the Ethiopian capital, Addis Ababa.
Title: Cosmic ray spectrum during Forbush decreases: Ground based
observations
Authors: Jämsen, T.; Usoskin, I. G.; Sakramo, J.; Kovaltsov, G. A.
Bibcode: 2006cosp...36.2298J
Altcode: 2006cosp.meet.2298J
Strong shocks propagating in the interplanetary medium sweep out
energetic cosmic rays leading to Forbush decreases of the cosmic ray
intensity Studying the cosmic ray spectrum during the times of Forbush
decreases would provide a tool for probing large scale interplanetary
irregularities However since the Forbush decreases are short transient
phenomena there is lack of information on detailed direct measurements
of the cosmic ray spectrum especially in the high energy range Here we
analyze the spectrum indirectly using simultaneous continuous cosmic ray
measurements in 2003-2005 at the ground in two nearby sites in Finland
by a neutron monitor in Oulu and by a muon scintillator detector in
Pyhasalmi Data from other neutron monitors are also used We showed
that the shock which sweeps out particles of all energies the fast
active phase of the Forbush decrease soon becomes transparent for high
energy particles leading to a faster recovery of more energetic cosmic
rays In some cases we observed a post-increase of cosmic rays in the
muon data the cosmic ray level at a late recovery phase exceeds the
pre-increase level We discussed some implications of the present study
in terms of the shocks development and interaction with cosmic rays
Title: Active longitudes, nonaxisymmetric dynamos and phase mixing
Authors: Berdyugina, S. V.; Moss, D.; Sokoloff, D.; Usoskin, I. G.
Bibcode: 2006A&A...445..703B
Altcode:
We discuss the problem of solar active longitudes from the viewpoint
of dynamo theory. We start from a recent observational analysis of the
problem undertaken by Berdyugina & Usoskin (2003, A&A, 405,
1121) and Usoskin et al. (2005, A&A, 441, 347) who demonstrated
from a study of sunspot data that solar active longitudes rotate
differentially, with a small but significant asynchrony between
northern and southern hemispheres. We suggest two concepts by which the
underlying magnetic structure could lead to the observed phenomenology -
the true differential rotation of a nonaxisymmetric magnetic structure
and a stroboscopic effect. In the latter case, a solid body rotation of
nonaxisymmetric magnetic structure is illuminated by an activity wave
propagating from middle latitudes to the solar equator, and so mimics a
differential rotation. We then discuss several mechanisms which could in
principle lead to the excitation of active longitudes. In particular,
we consider dynamo excitation of nonaxisymmetric magnetic modes,
nonaxisymmetric structures as a manifestation of a relic magnetic
field in the solar core, nonaxisymmetric solar hydrodynamics and
nonlinear instabilities that lack axial symmetry. We conclude that
these mechanisms all provide ways to explain the phenomenology,
provided the stroboscopic interpretation is accepted. Of course, a
quantitative explanation in the framework of any scenario requires
ultimately a detailed numerical simulation. The interpretation of
the available observations as a true differential rotation appears to
provide a much more severe challenge for theorists. We are unable to
suggest a plausible mechanism of this kind; however we can not exclude
in principle such an explanation. We relate the phenomenon of solar
active longitudes to the information available concerning stellar
active longitudes, and also consider evidence from other tracers of
solar activity.
Title: Heliospheric modulation of cosmic rays: Monthly reconstruction
for 1951-2004
Authors: Usoskin, Ilya G.; Alanko-Huotari, Katja; Kovaltsov, Gennady
A.; Mursula, Kalevi
Bibcode: 2005JGRA..11012108U
Altcode:
The differential energy spectrum of galactic cosmic rays in the
vicinity of the Earth can be parameterized by the so-called force
field model which has only one parameter, the modulation potential ϕ,
for a given local interstellar spectrum. Here we present the series
of monthly values of the modulation potential ϕ since February 1951,
reconstructed using the data from the worldwide neutron monitor network
and calibrated with precise balloon and space-borne direct measurements
of cosmic ray energy spectrum. This work provides a long series
of a parameter allowing for a quantitative estimate of the average
monthly differential energy spectrum of cosmic rays near the Earth. A
comparison with other occasional direct measurements of cosmic ray
spectra confirms the reliability of the present reconstruction. The
results can be applied in studies of long-term solar-terrestrial
relations and the global evolution of the heliosphere.
Title: What is Unusual About the 2005 January 20 SEP Event?
Authors: Gopalswamy, N.; Xie, H.; Yashiro, S.; Usoskin, I.
Bibcode: 2005AGUFMSH23A0318G
Altcode:
We report on the solar energetic particle (SEP) event of 2005 January
20 that had an associated ground level enhancement (GLE). The Solar
and Heliospheric Observatory (SOHO) spacecraft observed a CME, which
was among the fastest of cycle 23 CMEs. This event is consistent with
the results that the GLE-associated CMEs represent the fastest known
population of CMEs. A metric type II burst started before the proton
injection time, suggesting that a coronal shock was formed before
high-energy protons were released at the Sun. These 2005 January 20
event is consistent with the current paradigm that large SEP events
originate in CME-driven shocks. We also determined the height of
the CME at two time marks: the metric type II onset (2.1 Rs) and
the proton injection time (4.5 Rs). At a height of 4.5 Rs the CME
should have attained the maximum speed, thus driving the strongest
shocks. We discuss the estimation of the CME speed given that the
coronagraph observations were hampered by the SEPs arriving at the SOHO
spacecraft. We also discuss the arrival of the CME-associated plasma
and shock at 1 AU. Work supported by NASA/LWS and NSF/SHINE programs.
Title: Measurements of muon flux in the Pyhäsalmi underground
laboratory
Authors: Enqvist, T.; Mattila, A.; Föhr, V.; Jämsén, T.; Lehtola,
M.; Narkilahti, J.; Joutsenvaara, J.; Nurmenniemi, S.; Peltoniemi,
J.; Remes, H.; Sarkamo, J.; Shen, C.; Usoskin, I.
Bibcode: 2005NIMPA.554..286E
Altcode: 2005hep.ex....6032E
The cosmic-ray induced muon flux was measured at several depths in
the Pyhäsalmi mine (Finland) using a plastic scintillator telescope
mounted on a trailer. The flux was determined at four different
depths underground at 400 m (980 m.w.e), at 660 m (1900 m.w.e), at
990 m (2810 m.w.e) and at 1390 m (3960 m.w.e) with the trailer, and
also at the ground surface. In addition, previously measured fluxes
from depths of 90 m (210 m.w.e) and 210 m (420 m.w.e) are shown. A
relation was obtained for the underground muon flux as a function of
the depth. The measured flux follows well the general behaviour and
is consistent with results determined in other underground laboratories.
Title: Preferred sunspot longitudes: non-axisymmetry and differential
rotation
Authors: Usoskin, I. G.; Berdyugina, S. V.; Poutanen, J.
Bibcode: 2005A&A...441..347U
Altcode: 2005astro.ph..8422U
As recently found, the distribution of sunspots is non-axisymmetric
and spot group formation implies the existence of two persistent
active longitudes separated by 180°. Here we quantitatively study the
non-axisymmetry of sunspot occurrence. In a dynamic reference frame
inferred from the differential rotation law, the raw sunspot data
show a clear clustering around the persistent active longitudes. The
differential rotation describing the dynamic frame is quantified
in terms of the equatorial angular velocity and the differential
rotation rate, which appear to be significantly different from those
for individual sunspots. This implies that the active longitudes are
not linked to the depth of sunspot anchoring. In order to quantify
the observed effect, we introduce a measure of the non-axisymmetry of
the sunspot distribution. The non-axisymmetric component is found to
be highly significant, and the ratio of its strength to that of the
axisymmetric one is roughly 1:10. This provides additional constraints
for solar dynamo models.
Title: Solar activity, cosmic rays, and Earth's temperature: A
millennium-scale comparison
Authors: Usoskin, I. G.; Schüssler, M.; Solanki, S. K.; Mursula, K.
Bibcode: 2005JGRA..11010102U
Altcode:
Previous studies of a solar influence on climate variations have often
suffered from the relatively short length of continuous direct solar
observations of less than 400 years. We use two recently reconstructed
series of the sunspot number and the cosmic ray flux to study this
question over time intervals of up to nearly 1800 years. Comparison of
the Sun-related data sets with various reconstructions of terrestrial
Northern Hemisphere mean surface temperatures reveals consistently
positive correlation coefficients for the sunspot numbers and
consistently negative correlation coefficients for the cosmic rays. The
significance levels reach up to 99% but vary strongly for the different
data sets. The major part of the correlation is due to the similarity
of the long-term trends in the data sets. The trend of the cosmic ray
flux correlates somewhat better with the terrestrial temperature than
the sunspot numbers derived from the same cosmogenic isotope data.
Title: Climate: How unusual is today's solar activity? (reply)
Authors: Solanki, S. K.; Usoskin, I. G.; Kromer, B.; Schüssler, M.;
Beer, J.
Bibcode: 2005Natur.436E...4S
Altcode:
Muscheler et al. claim that the solar activity affecting cosmic rays
was much higher in the past than we deduced from 14C
measurements. However, this claim is based on a problematic
normalization and is in conflict with independent results, such as
the 44Ti activity in meteorites and the 10Be
concentration in ice cores.
Title: Solar activity over the last 1150 years: does it correlate
with climate?
Authors: Usoskin, I. G.; Schüssler, M.; Solanki, S. K.; Mursula, K.
Bibcode: 2005ESASP.560...19U
Altcode: 2005csss...13...19U
No abstract at ADS
Title: Real-Time Cosmic Ray Distributed (RECORD) database: A status
report
Authors: Starodubtsev, S. A.; Turpanov, A. A.; Kudela, K.; Usoskin,
I. G.; Yanke, V. G.; Grigoryev, V. G.; Neustroyev, N. I.; Egorov,
A. G.; Prikhodko, A. N.
Bibcode: 2005ICRC....2..465S
Altcode: 2005ICRC...29b.465S
No abstract at ADS
Title: Long-Term Modulation of the Cosmic Ray Fluctuation Spectrum:
Spacecraft Measurements
Authors: Starodubtsev, S. A.; Usoskin, I. G.; Grigoryev, A. V.;
Mursula, K.
Bibcode: 2005ICRC....2..247S
Altcode: 2005ICRC...29b.247S
No abstract at ADS
Title: Coronal Mass Ejections and Ground Level Enhancements
Authors: Gopalswamy, N.; Xie, H.; Yashiro, S.; Usoskin, I.
Bibcode: 2005ICRC....1..169G
Altcode: 2005ICRC...29a.169G
No abstract at ADS
Title: The role of drifts in the galactic cosmic ray transport
Authors: Alanko, K.; Usoskin, I. G.; Mursula, K.
Bibcode: 2005ICRC....2...53A
Altcode: 2005ICRC...29b..53A
No abstract at ADS
Title: Cosmic ray-induced ionization in the atmosphere: spatial and
temporal changes
Authors: Usoskin, I. G.; Gladysheva, O. G.; Kovaltsov, G. A.
Bibcode: 2004JASTP..66.1791U
Altcode: 2004JATP...66.1791U
Detailed calculations of the time-variable spatial distribution of
cosmic ray-induced ionization of the lower atmosphere are presented
using a physical model. Using the differential energy spectrum of cosmic
rays obtained from the worldwide neutron monitor network since 1951 and
taking into account also the slow changes in the geomagnetic dipole,
we have calculated the corresponding 3D (geographical coordinates and
altitude) equilibrium ion concentration in the lower atmosphere as a
function of time for the period 1951-2000. A comparison to the results
of measurements validates the calculation method, as the calculated
cosmic ray-induced ionization reproduces in general the observed
altitudinal and latitudinal profiles of the ion concentration. The
results of the present work provide a basis for a quantitative study
of the solar-terrestrial relationships on long time scales.
Title: An Upper Limit on Sunspot Activity During the Maunder Minimum
Authors: Kovaltsov, G. A.; Usoskin, I. G.; Mursula, K.
Bibcode: 2004SoPh..224...95K
Altcode: 2005SoPh..224...95K
We have estimated the upper and lower limits of sunspot activity, in
terms of active day fraction during the Maunder minimum (1645-1710),
using raw information on individual daily observations (Hoyt and
Schatten, 1998). Establishing the relation between the sunspot
activity and active day fraction after 1850, we evaluate the upper
limit of annual group sunspot number during the deep Maunder minimum
(1645-1700) which does not exceed 4. The earlier finding of a dominant
22-year periodicity during the Maunder minimum is verified and shown
to be robust. Also we confirm that the start of the Maunder minimum
was very abrupt.
Title: Rapid Cosmic Ray Fluctuations: Evidence for Cyclic Behaviour
Authors: Starodubtsev, S. A.; Usoskin, I. G.; Mursula, K.
Bibcode: 2004SoPh..224..335S
Altcode: 2005SoPh..224..335S
We study rapid cosmic-ray fluctuations using 5-min resolution data
from eight neutron monitors with different cutoff rigidities as well
as from the ACE satellite. We define a proxy index of rapid cosmic-ray
fluctuations as the mean power of the cosmic-ray power spectrum in the
frequency range 10−4 −1.67 × 10−3 Hz (10
min to about 3 h). A dominant 11-year periodicity in the index is found
in all neutron monitors. We also report on intermittent, short-term
periodicities in the power of rapid cosmic-ray fluctuations. A strong
mid-term periodicity of about 1.6 - 1.8 years, possibly related to a
recently found similar periodicity in IMF, appears in CR fluctuation
power since the 1980s. Another strong periodicity is found at 1 year,
which is likely related to the relative position of the Earth in the
heliosphere. These results also provide new challenge to test the
cosmic-ray modulation theory.
Title: Preface
Authors: mursula, kalevi; usoskin, ilya; cliver, edward
Bibcode: 2004SoPh..224....3M
Altcode: 2005SoPh..224....3M
No abstract at ADS
Title: Long-Term Solar Activity: Direct and Indirect Study
Authors: Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2004SoPh..224...37U
Altcode: 2005SoPh..224...37U
The series of directly observed sunspot numbers is nearly 400 years
long. We stress that the recently compiled group sunspot number series
is an upgrade of the old Wolf series and should always be used before
1850. The behavior of solar activity on longer time scales can be
studied only using indirect proxies. Such proxies as aurorae occurrence
or naked-eye sunspot observations are qualitative indicators of solar
activity but can be hardly quantitatively interpreted. Cosmogenic
isotope records provide a basis for quantitative estimate of the past
solar activity. Here we overview the main methods of the long-term
solar activity reconstruction on the centennial to multimillennia
time scale. We discuss that regression-based reconstructions of solar
activity lead to very uncertain results, while recently developed
physics-based models raise solar activity reconstruction to a new level
and allow studying its behavior on a multimillennia time scale. In
particular, the reconstructions show that the recent episode of high
solar activity is quite unusual in the multimillennia time scale.
Title: Unusual activity of the Sun during recent decades compared
to the previous 11,000 years
Authors: Solanki, S. K.; Usoskin, I. G.; Kromer, B.; Schüssler, M.;
Beer, J.
Bibcode: 2004Natur.431.1084S
Altcode:
Direct observations of sunspot numbers are available for the past
four centuries, but longer time series are required, for example,
for the identification of a possible solar influence on climate
and for testing models of the solar dynamo. Here we report a
reconstruction of the sunspot number covering the past 11,400 years,
based on dendrochronologically dated radiocarbon concentrations. We
combine physics-based models for each of the processes connecting
the radiocarbon concentration with sunspot number. According to our
reconstruction, the level of solar activity during the past 70 years is
exceptional, and the previous period of equally high activity occurred
more than 8,000 years ago. We find that during the past 11,400 years
the Sun spent only of the order of 10% of the time at a similarly high
level of magnetic activity and almost all of the earlier high-activity
periods were shorter than the present episode. Although the rarity
of the current episode of high average sunspot numbers may indicate
that the Sun has contributed to the unusual climate change during the
twentieth century, we point out that solar variability is unlikely
to have been the dominant cause of the strong warming during the past
three decades.
Title: Latitudinal dependence of low cloud amount on cosmic ray
induced ionization
Authors: Usoskin, I. G.; Marsh, N.; Kovaltsov, G. A.; Mursula, K.;
Gladysheva, O. G.
Bibcode: 2004GeoRL..3116109U
Altcode: 2004physics...7066U
A significant correlation between the annual cosmic ray flux and
the amount of low clouds has recently been found for the past 20
years. However, of the physical explanations suggested, none has
been quantitatively verified in the atmosphere by a combination
of modelling and experiment. Here we study the relation between
the global distributions of the observed low cloud amount and the
calculated tropospheric ionization induced by cosmic rays. We find
that the time evolution of the low cloud amount can be decomposed into
a long-term trend and inter-annual variations, the latter depicting
a clear 11-year cycle. We also find that the relative inter-annual
variability in low cloud amount increases polewards and exhibits a
highly significant one-to-one relation with inter-annual variations
in the ionization over the latitude range 20-55°S and 10-70°N. This
latitudinal dependence gives strong support for the hypothesis that
the cosmic ray induced ionization modulates cloud properties.
Title: Solar Modulation Models:. a Comparison Through a 2d Stochastic
Simulation
Authors: Bobik, P.; Gervasi, M.; Grandi, D.; Rancoita, P. G.; Usoskin,
I. G.
Bibcode: 2004apsp.conf...23B
Altcode:
We developed a 2D stochastic simulation model of galactic cosmic rays
propagation in the heliosphere. Drift effects are taken in account in
the solar modulation model. The model has been optimized by comparison
with measured data. We also analyze the dependence of the modulated
flux of cosmic rays at 1 AU from the diffusion tensor, and its relation
with the solar cavity and cosmic rays parameters. We compute spectra
for different values of the tilt angle for both positive and negative
solar cycles.
Title: Usoskin et al. Reply:
Authors: Usoskin, Ilya G.; Solanki, Sami K.; Schüssler, Manfred;
Mursula, Kalevi
Bibcode: 2004PhRvL..92s9002U
Altcode:
A Reply to the Comment by G. M. Raisbeck and F. Yiou.
Title: Persistent active longitudes in the surface magnetic activity
on the Sun
Authors: Berdyugina, S.; Usoskin, I. G.
Bibcode: 2004cosp...35.1722B
Altcode: 2004cosp.meet.1722B
A novel analysis of sunspot data for the past 120 years reveals
that sunspots in both northern and southern hemispheres are formed
preferably in two persistent active longitudes separated by 180°. In
the Carrington reference frame, the active longitudes continuously
migrate in phase with respect to the Carrington meridian. The
migration of the active longitudes is determined by changes of the mean
latitude of sunspots and the surface differential rotation. The two
active longitudes periodically alternate being the dominant region,
similar to the 'flip-flop' phenomenon known in starspot activity. The
period of the oscillations is about 3.8 and 3.65 years in the northern
and southern hemispheres, respectively. The difference between the
periods is significant and can be related to the known north-south
asymmetry in the solar magnetic activity. Similar results are obtained
from the analysis of large-scale surface magnetic fields using solar
magnetic synoptic maps, for the cycles 20 to 23. The persistent active
longitudes 180° apart, which migrate with the surface differential
rotation and alternate their activity level with the 3.7-yr cycle, are
found separately in positive and negative polarity fields. Our results
provide new observational constraints for current solar dynamo models
and strengthen the solar paradigm for magnetic activity on cool stars.
Title: Cosmic ray induced ionization in the troposphere: Numerical
model
Authors: Usoskin, I. G.; Gladysheva, O. G.; Kovaltsov, G. A.
Bibcode: 2004cosp...35.1671U
Altcode: 2004cosp.meet.1671U
First detailed calculations of the time-variable spatial distribution
of cosmic ray induced ionization of the lower atmosphere are
presented using a physical model describing development of a
nucleonic-electromagnetic cascade in the atmosphere. Using the
differential energy spectrum of cosmic rays obtained from the worldwide
neutron monitor network data since 1951 and taking into account also
the slow changes in the geomagnetic field, we have calculated the
corresponding 3D (geographical coordinates and altitude) equilibrium
ion concentration in the lower atmosphere as a function of time for the
period 1951-2000. A comparison with the results of actual balloon-borne
measurements of the atmospheric ionization validates the calculation
method, and the calculated cosmic ray induced ionization reproduces the
observed altitudinal and latitudinal profiles of the ion concentration
for the altitude range 0-12 km. The results of the present work provide
a basis for quantitative study of the solar-terrestrial relationships
on long time scales.
Title: Cosmic ray modulation and global heliospheric parameters:
Non-linear relations
Authors: Usoskin, I. G.; Kovaltsov, G. A.; Mursula, K.; Alanko, K.
Bibcode: 2004cosp...35.1685U
Altcode: 2004cosp.meet.1685U
Despite the great success of sophisticated cosmic ray modulation models,
the heliospheric modulation strength is still a useful parameter
for formal description of the long-term modulation of cosmic rays,
which alone defines shape of the cosmic ray energy spectrum in the
neutron monitor energy range. Annual averaged values of the modulation
strength have recently been computed for the neutron monitor era
since 1951-2002 (Usoskin et al., Sol. Phys., 207, 389, 2002). Here we
study a physics-based semi-empirical, non-linear relation between the
modulation strength and the following global heliospheric parameters:
the heliospheric current sheet tilt angle, the open solar magnetic
flux and the global magnetic field polarity. The suggested relation,
which includes four fitting parameters, reproduces the measured
annual NM count rates within the accuracy of 0.8%. Using the measured
interplanetary magnetic field parameters and the modulation strength
values computed since 1951, this relation allows us to reconstruct
the annual tilt angle for about 20 years before the time of direct
measurements of the tilt angle.
Title: Persistent Active Longitudes in Sunspot Activity: Sun-as-a-Star
Approach
Authors: Berdyugina, S. B.; Usoskin, I. G.
Bibcode: 2004IAUS..219..128B
Altcode: 2003IAUS..219E.183B
An analysis of sunspot group data for the past 120 years reveals
that sunspots are formed preferably in two persistent migrating
active longitudes 180 degrees apart. Their migration is determined by
changes of the mean latitude of sunspots and the surface differential
rotation. The two active regions periodically alternate being the
dominant region with a period of about 3.5-3.7 years similar to the
""flip-flop"" phenomenon known in starspot activity. The fact that the
Sun shows the same pattern of magnetic activity as highly active stars
strengthens the solar paradigm for magnetic activity on cool stars
allowing the physics of the activity on such stars to be understood
within the context of the physical principles deduced from the study
of the Sun.
Title: Reconstruction of solar activity for the last millennium
using 10Be data
Authors: Usoskin, I. G.; Mursula, K.; Solanki, S.; Schüssler, M.;
Alanko, K.
Bibcode: 2004A&A...413..745U
Altcode: 2003astro.ph..9556U
In a recent paper (Usoskin et al. 2002a), we have reconstructed
the concentration of the cosmogenic 10Be isotope in ice
cores from the measured sunspot numbers by using physical models
for 10Be production in the Earth's atmosphere, cosmic ray
transport in the heliosphere, and evolution of the Sun's open magnetic
flux. Here we take the opposite route: starting from the 10Be
concentration measured in ice cores from Antarctica and Greenland, we
invert the models in order to reconstruct the 11-year averaged sunspot
numbers since 850 AD. The inversion method is validated by comparing
the reconstructed sunspot numbers with the directly observed sunspot
record since 1610. The reconstructed sunspot record exhibits a prominent
period of about 600 years, in agreement with earlier observations
based on cosmogenic isotopes. Also, there is evidence for the century
scale Gleissberg cycle and a number of shorter quasi-periodicities
whose periods seem to fluctuate in the millennium time scale. This
invalidates the earlier extrapolation of multi-harmonic representation
of sunspot activity over extended time intervals.
Title: Establishing space research capability in Ethiopia
Authors: Bosinger, T.; Damtie, B.; Usoskin, I. G.
Bibcode: 2004cosp...35.2504B
Altcode: 2004cosp.meet.2504B
It is often considered by various sources and institutions around the
world that promotion of space physics activities in a developing country
like Ethiopia is a waste of time and resources. It has, of course, some
sense: developing countries should put all their efforts in improving
the standard of life, infrastructure and basic education. However,
it is straightforward to realize that nowadays improvement in any of
the basic needs of developing countries is related to high technology
(e.g. mobile phones, GPS, remote sensing). This means that a developing
country has to take care of recruiting specialists among their own
people who can take part in the decision making processes which are
increasingly of global nature. Moreover, many citizens of developing
countries are studying and working abroad attaining high expertise. As
a matter of fact, there are more Ethiopians with PhD in physics working
abroad than in the country. These people are lost for the benefit of
their own country if there is no need for their profession in their
home country. There is no doubt that the main task of improving the
standard of living cannot be achieved without development and social
transformation of the society, which can take place efficiently in a
self-adopting and dynamic process. In line with the above argument, we
have initiated the establishment of the Washera Space Physics Laboratory
(WASPL) at Addis Ababa University in Ethiopia. It is a collaboration
project between Oulu University and Addis Ababa University. The
laboratory is expected to start operation of a pulsation magnetometer
and photometer in September 2004. Other types of standard geophysical
instruments are to be installed in subsequent missions. The project is
of mutual interest of both parties. The equatorial ionosphere is still a
poorly investigated region of our near Earth's space. In a first pilot
investigation the existence and properties of the ionospheric Alfvén
resonator (IAR) in the equatorial ionosphere is addressed. WASPL is
expected to join worldwide activities in monitoring local and global
atmosphereic and ionospheric parameters. There is also a plan to install
a neutron monitor to measure galactic and solar cosmic rays. WASPL will
be situated at the magnetic equator and at 2500m above seal level, which
make it a unique place to carry out space physics experiments. In this
paper, we describe WASPL in some more details. Interested scientists
may participate with us and/or start similar initiatives.
Title: Long-term variations in cosmic ray fluctuations
Authors: Starodubtsev, S. A.; Usoskin, I. G.; Mursula, K.
Bibcode: 2004cosp...35.1930S
Altcode: 2004cosp.meet.1930S
It has been shown recently that the level of cosmic ray fluctuations
varies over a solar cycle due to the corresponding changes of the in
interplanetary turbulence spectrum. In earlier studies, fragmentary
high-resolution data from polar neutron monitors (Tixie Bay and
Oulu) were used. Here we present the results of an analysis of 5-min
resolution cosmic ray data series from six neutron monitors with
geomagnetic cutoff rigidities from polar to 6 GV (Calgary, Kiel,
Lomnicky Stit, Oulu, Rome and Tixie) as well as from space-borne
IMP-8. The longest time series of 5-min data is from Oulu NM
since 1968. As the index of cosmic ray fluctuations we use the
mean power of the cosmic ray power spectrum in the frequency range
10-4-1.67\cdot 10-3 Hz. The dominant 11-year
periodicity is found in all series, confirming earlier results but
in a wide range of cutoff rigidities. We report also new persistent
periodicities in cosmic ray fluctuations. A strong 1.5-1.8-year
periodicity related the corresponding cyclicities in IMF is apparent
in all data series. Another strong peak is found at nearly 1 year
period, which is related to the relative position of the Earth in the
heliosphere. These results provide a new basis for testing the cosmic
ray modulation theory.
Title: Low cloud amount vs. Cosmic ray induced ionization: One-to-one
relation
Authors: Usoskin, I. G.; Marsh, N.; Mursula, K.; Gladysheva, O. G.;
Kovaltsov, G. A.
Bibcode: 2004cosp...35.1683U
Altcode: 2004cosp.meet.1683U
A highly significant correlation between the annual flux of cosmic
rays at the Earth's orbit and the amount of low clouds has recently
been found for the past 20 years. However, a comprehensive physical
explanation still remains elusive. Elsewhere in this session we present
a numerical model to calculate ionization of the troposphere caused by
a cosmic ray induced nucleonic-electromagnetic cascade. Here we study
the relation between this calculated cosmic ray induced ionization
and the global distributions of the observed low cloud amount. We find
that the time evolution of the low cloud amount can be decomposed into
a long-term trend and inter-annual variations, the latter depicting a
clear 11-year cycle with very strong correlation (r=0.84) with cosmic
ray induced ionization. We also find that the relative inter-annual
variability in low cloud amount increases polewards and exhibits a
highly significant one-to-one relation with inter-annual variations in
the ionization over the latitude range 20--55° S and 10--70° N. This
latitudinal dependence gives strong support for the hypothesis that
cosmic ray induced ionization modulates cloud properties.
Title: Streaming of Galactic Cosmic Rays in the Heliosphere and the
Role of Drifts
Authors: Alanko, K.; Usoskin, I. G.; Mursula, K.
Bibcode: 2004cosp...35.2250A
Altcode: 2004cosp.meet.2250A
During their transport through the heliosphere, galactic cosmic rays
suffer from scattering on magnetic inhomogenities, from convection
and adiabatic cooling by the solar wind. In addition to these basic
mechanisms, also drifts (gradient, curvature and drift along the wavy
heliospheric current sheet) affect the transport of cosmic rays. All
these effects are known as the solar modulation of cosmic rays. We have
recently presented a new model of the transport of galactic cosmic rays
in a 2D axisymmetric heliosphere, which includes the above mentioned
effects. Using this model, we can compare the effects of different
modulation mechanisms in the model and, in particular, study the role
of drifts. We also study the streaming of galactic cosmic rays inside
the heliosphere, their modulated spectra, the time particles spend in
the heliosphere and the modulation function.
Title: Solar activity and climate during the last millennium
Authors: Solanki, S. K.; Usoskin, I.; Schüssler, M.
Bibcode: 2004cosp...35.2535S
Altcode: 2004cosp.meet.2535S
The sunspot number is the longest running direct index of solar
activity, with direct measurements starting in 1610. For many purposes,
e.g., for comparisons with climate indices, it is still too short. We
present a reconstruction of the cycle-averaged sunspot number over the
last millennium based on 10Be concentrations in Greenland
and Antarctic ice cores. As intermediate steps of the method, we also
reconstruct the cosmic ray flux at Earth and the Sun's open magnetic
flux. The reconstructions are validated by comparison with direct
measurements or independent reconstructions. We also compare with
records of global climate, in particular with the global temperature
("hockey stick") curve of Mann et al (1998). A reasonable agreement
is found for the entire millennium, excluding only the last decades,
when the two curves start diverging from each other.
Title: Magnetic Activity Cycles on the Sun and Stars
Authors: Usoskin, I. G.; Berdyugina, S.
Bibcode: 2004cosp...35.1721U
Altcode: 2004cosp.meet.1721U
Cycles of magnetic activity on the Sun and stars are manifestations
of a magnetic dynamo, which is one of the most interesting processes
in solar/stellar astrophysics. Evolution of solar magnetic cycles is
studied for several centuries including the nearly spotless Maunder
minimum and recent super-active cycles, thanks to tremendous work
of R. Wolf and his successors and later D. Hoyt and K. Schatten who
complied sunspot record series. Magnetic cycles in stars are studied
during few decades but they provide a large ensemble statistics
due to a large number of studied stars. Here we review most recent
achievements and findings in studies of solar/stellar magnetic cycles,
such as determinism and chaos in the cyclicity, cycles during active
phases and great minima, active longitudes and 'flip-flop' cycles,
occurrence of great minima and super-active periods.
Title: Reconstruction of Monthly and Yearly Group Sunspot Numbers
From Sparse Daily Observations
Authors: Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2003SoPh..218..295U
Altcode:
Some periods before 1820 are poorly covered by sunspot observations. In
addition to apparent, long observational gaps, there are also
periods when there are only few sparse daily sunspot observations
during a long time. It is important to estimate the reliability of
the monthly and yearly mean sunspot values obtained from such sparse
daily data. Here we suggest a new method to estimate the reliability of
individual monthly means. The method is based on comparing the actual
sparse data (sample population) to the well-measured sunspot data in
1850-1996 (reference population), and assumes that the statistical
properties of sunspot activity remain similar throughout the entire
period. For each sample population we first found those months in the
reference population that contain the same data set, and constructed
the statistical distribution of the corresponding monthly means. The
mean and standard error of this distribution represent the mean and
uncertainty of a monthly mean sunspot number reconstructed from sparse
daily observations. The simple arithmetic mean of daily values can
be adequately applied for months which contain more than 4-5 evenly
distributed daily observations. However, the reliability of monthly
means for less covered months has to be estimated more carefully. Using
the estimated, new monthly values, we have also calculated the weighted
annual sunspot numbers.
Title: Long-Term Solar Cycle Evolution: Review of Recent Developments
Authors: Usoskin, I. G.; Mursula, K.
Bibcode: 2003SoPh..218..319U
Altcode:
The sunspot number series forms the longest directly observed index
of solar activity and allows one to trace its variations on the time
scale of about 400 years since 1610. This time interval covers a wide
range from seemingly vanishing sunspots during the Maunder minimum in
1645-1700 to the very high activity during the last 50 years. Although
the sunspot number series has been studied for more than a century, new
interesting features have been found even recently. This paper gives a
review of the recent achievements and findings in long-term evolution
of solar activity cycles such as determinism and chaos in sunspot
cyclicity, cycles during the Maunder minimum, a general behaviour of
sunspot activity during a great minimum, the phase catastrophe and
the lost cycle in the beginning of the Dalton minimum in 1790s and
persistent 22-year cyclicity in sunspot activity. These findings shed
new light on the underlying physical processes responsible for sunspot
activity and allow a better understanding of such empirical rules as
the Gnevyshev-Ohl rule and the Waldmeier relations.
Title: Millennium-Scale Sunspot Number Reconstruction: Evidence for
an Unusually Active Sun since the 1940s
Authors: Usoskin, Ilya G.; Solanki, Sami K.; Schüssler, Manfred;
Mursula, Kalevi; Alanko, Katja
Bibcode: 2003PhRvL..91u1101U
Altcode: 2003astro.ph.10823U
The extension of the sunspot number series backward in time is of
considerable interest for dynamo theory, solar, stellar, and climate
research. We have used records of the 10Be concentration in
polar ice to reconstruct the average sunspot activity level for the
period between the year 850 to the present. Our method uses physical
models for processes connecting the 10Be concentration with
the sunspot number. The reconstruction shows reliably that the period
of high solar activity during the last 60years is unique throughout
the past 1150years. This nearly triples the time interval for which
such a statement could be made previously.
Title: 2D stochastic simulation model of cosmic ray modulation:
comparison with experimental data
Authors: Bobik, P.; Gervasi, M.; Grandi, D.; Rancoita, P. G.; Usoskin,
I. G.
Bibcode: 2003ESASP.535..637B
Altcode: 2003iscs.symp..637B
We developed a 2D stochastic simulation model for heliospheric
propagation of galactic cosmic rays. The model solves numerically the
transport equation of particles in the heliosphere. In the calculation
we use also drift effects which are included through analytical
effective drift velocities. We estimated the cosmic rays spectrum at
1 AU using this model formalism. The calculated spectra are compared
with other models (CREME96) and with experimental data (IMP8 and AMS)
for positive (A>0) and negative (A<0) solar periods.
Title: Long-Term Modulation of the Galactic Cosmic-Ray Fluctuation
Spectrum
Authors: Starodubtsev, S. A.; Usoskin, I. G.
Bibcode: 2003AstL...29..594S
Altcode:
We study the temporal behavior of the power spectra for Galactic
cosmic-ray fluctuations during the last two solar cycles. We use the
5-min data for 1980-2002 corrected for the barometric effect from two
widely separated high-latitude cosmic-ray stations, Tixie Bay and
Oulu. The cosmic-ray fluctuation spectrum is shown to be subjected
to a regular long-term modulation with a period of about 11 years in
phase with the solar cycle, in accordance with the variations in the
inertial part of the turbulence spectrum for the interplanetary magnetic
field. Based on independent measurements, we confirm the previously
detected cosmic-ray fluctuation power enhancement at the maximum of
the 11-year solar cycle and its subsequent decrease at minimum solar
activity using new, more extensive data sets. We reach the conclusion
about the establishment of a new cosmic-ray modulation phenomenon that
has not been described previously in scientific literature.
Title: On the reliability of monthly/yearly means calculated from
sparse daily sunspot numbers
Authors: Usoskin, Ilya G.; Mursula, Kalevi; Kovaltsov, Gennady A.
Bibcode: 2003ESASP.535..165U
Altcode: 2003iscs.symp..165U
Some periods before 1850 are poorly covered by sunspot observations. In
addition to apparent observational gaps, there are also periods when
there are only few sparse daily sunspot observations during a long
time. It is important to estimate the reliability of the monthly/yearly
mean values obtained from sparse daily data. Here we suggest a new
method to estimate the reliability of individual monthly means. The
method is based on comparing the actual sparse data (sample population)
to the well-measured sunspot data in 1850-1996 (reference population)
and employs two assumptions: (I) statistical properties of sunspot
activity are similar throughout the entire period and (II) individual
sparse daily observations are distributed randomly in time. First,
for each sample population we found months in the reference population
containing the same data set and then constructed the statistical
distribution of the corresponding monthly means. From this distribution
we calculated the weighted mean and its standard error which gives
the uncertainty of a monthly mean sunspot number reconstructed from
sparse daily observation. The simple arithmetic mean can be adequately
applied for months which contain more than 4-5 evenly distributed daily
observations. However, the reliability of monthly means for less covered
months should be estimated more carefully. Using the estimated monthly
values, we can also calculate the weighted annual sunspot numbers.
Title: The lost sunspot cycle: reanalysis of sunspot statistics
Authors: Usoskin, Ilya G.; Mursula, Kalevi; Kovaltsov, Gennady A.
Bibcode: 2003ESASP.535..161U
Altcode: 2003iscs.symp..161U
We have recently suggested (Usoskin et al., 2000) that one low sunspot
cycle was possibly lost in 1790s, and argued (Usoskin et al., 2002) that
the existence of such a cycle does not contradict with available solar
proxies, like auroral observations and cosmogenic isotopes. However,
some arguments based on a statistical analysis of sunspot activity have
been presented against the lost cycle (Krivova et al., 2002). Since the
consequences of a new cycle are significant for solar cycle studies,
it is important to try to estimate the probability of such a cycle to
exist. Here we present the results of a rigorous statistical analysis
of all available sunspot observations around the suggested additional
cycle minimum in 1792-1793. We show that the level of sunspot activity
in 1792-1793 is statistically similar to that in the minimum phase,
but significantly different from that in the mid-declining or maximum
phases. Using the estimated uncertainties we also calculate new,
weighted annual values of group sunspot numbers in 1790-1796 which show
a clear minimum in 1792-1793 and a maximum in 1794-1795, supporting
the idea of an additional weak cycle in 1790's.
Title: Neutron monitor database in real time
Authors: Kozlov, Valery; Kudela, Karel; Starodubtsev, Sergei; Turpanov,
Alexey; Usoskin, Ilya; Yanke, Victor
Bibcode: 2003ESASP.535..675K
Altcode: 2003iscs.symp..675K
A first distributed Real Time Cosmic Ray Database using measurements
of several neutron monitors is presented. The aim of the project is to
develop a unified database with data from different neutron monitors
collected together, in unified format and to provide a user with several
commonly used data access methods. The database contains original
cosmic ray as well as all housekeeping and technical data necessary
for scientific data analysis. Currently the database includes Lomnicky
Stit, Moscow, Oulu, Tixie Bay, Yakutsk stations and it is opened for
other neutron monitors. The main database server is located in IKFIA
SB RAS (Yakutsk) but there will be several mirrors of the database. The
datbase and all its mirrors are updated on the nearly real-time (1 hour)
basis. The data access software includes WWW-interface, Perl scipts and
C library, which may be linked to a user program. Most of frequently
used functions are implemented to make it operable to users without
SQL language knowledge. A draft of the data representation standard is
suggested, based on common practice of neutron monitor community. The
database engine is freely distributed open-sourced PostgreSQL server
coupled with a set of replication tools developed at Bioengineering
division of the IRCCS E. Medea, Italy.
Title: New standpoints in long-term solar cycle evolution: a review
Authors: Usoskin, I. G.; Mursula, K.
Bibcode: 2003ESASP.535...25U
Altcode: 2003iscs.symp...25U
The sunspot number series forms the longest directly observed index of
solar activity and allows to trace its variations on the time scale of
about 400 years since 1610. This time interval covers a wide range from
seemingly vanishing sunspots during the Maunder minimum in 1645-1700
to the very high activity during the last 500 years. Although the
sunspot number series has been studied for more than a century, new
interesting features can still be found. This paper gives a review of
the recent achievements and findings in long-term evolution of solar
activity cycles such as determinism and chaos in sunspot cyclicity,
cycles during the Maunder minimum, scenario of a great minimum, the
phase catastrophe and the lost cycle in the beginning of the Dalton
minimum in 1790s and persistent 22-year cyclicity. These findings shed
new light on the underlying physical processes responsible for the
sunspot activity and allow for better understanding of such empirical
rules as Gnevyshev-Ohl rule and Waldmeier relations.
Title: Heliospheric modulation strength: effective neutron monitor
energy
Authors: Alanko, K.; Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2003AdSpR..32..615A
Altcode:
The widely used concept of the neutron monitor energy range is not
well defined. Also, the median energy of a neutron monitor varies in
the course of the solar cycle. Here we present a new concept of the
effective energy of cosmic rays as measured by neutron monitors. Using
a spherically-symmetric model of the heliospheric transport of cosmic
rays and the specific yield function of a neutron monitor, we show that
there is such an effective energy that the count rate of a given neutron
monitor is directly proportional to the flux of cosmic rays with energy
above this effective energy, irrespectively of the phase of the solar
cycle. The new concept of the effective energy allows to regard the
neutron monitor count rate as a direct measurement of the galactic
cosmic ray flux with energy above this value. The effective energy
varies from about 6 GeV for polar up to about 50 GeV for equatorial
stations (e.g., it is about 6.5 GeV for high-latitude Oulu, 8 GeV for
mid-latitude Climax and 40 GeV for equatorial Huancayo NM).
Title: Effective Energy of Neutron Monitors
Authors: Alanko, K. M.; Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2003ICRC....7.3901A
Altcode: 2003ICRC...28.3901A
The widely used concept of the neutron monitor energy range is not
well defined. Also, the median energy of a neutron monitor varies in
the course of the solar cycle. Here we present a new concept of the
effective energy of cosmic rays measured by neutron monitors. Using
a 1D model of the heliospheric transport of cosmic rays and the
specific yield function of a neutron monitor, we show that there is
such an energy value, here called the effective energy, that the
count rate of a given neutron monitor is directly proportional to
the flux of cosmic rays with energy above this effective energy,
irresp ective of the phase of the solar cycle. The new concept of
the effective energy allows to regard the count rate of each neutron
monitor as a direct measurement of the galactic cosmic ray flux with
energy above the effective energy specified for tha station. The
effective energy varies from about 5.5 GeV for polar up to about 20
GeV for equatorial stations. The effective energy for the cosmogenic
polar 10 Be and global 14 C production is about 1.3 GeV and 2.8 GeV,
respectively. The data of the world-wide network of neutron monitors
(NMs) provide a good, stable and consistent data set of galactic
cosmic ray (GCR) intensities for more than 50 years. However, a NM is
an integral device measuring all cosmic rays above a certain energy
(local geomagnetic or atmospheric rigidity cutoff ) with the yield
function increasing sharply with energy. Therefore, it is not clear
what is the effective energy of cosmic rays as measured by NM. In
this paper, we intro duce a concept of the effective energy of a NM,
Eef f , so that the count rate of a given neutron monitor is directly
proportional to the flux of cosmic rays with energy above this effective
energy, irresp ectively of the phase of solar cycle. In other words,
variations of NM count rate directly corresp ond to variations of the
GCR flux above this effective energy. Neutron monitor count rates can
be obtained as follows: ∞ G(T , t) · Y (T , x) · dT N (Pc , x, t) =
(1) Pc
Title: A 2D Stochastic Simulation of Galactic Cosmic Rays Transport
in the Heliosphere
Authors: Alanko, K. M.; Usoskin, Ilya; Mursula, Kalevi; Kovaltsov,
Gennady A.
Bibcode: 2003ICRC....7.3851A
Altcode: 2003ICRC...28.3851A
We present a new code to numerically simulate the transport of galactic
cosmic rays in a 2D axisymmetric heliosphere. The model solves the
transport equation by sto chastic simulation techniques, tracing
trajectories of test particles in a guiding center approximation. It
includes such basic modulation mechanisms as diffusion, convection and
adiabatic cooling. We present the first results from this model and
compare the effects of the different modulation mechanisms in the model.
Title: Galactic Cosmic Ray Fluctuations: Long-Term Modulation of
Power Spectrum
Authors: Usoskin, Ilya G.; Starodubtsev, S.
Bibcode: 2003ICRC....7.3905S
Altcode: 2003ICRC....7.3905U; 2003ICRC...28.3905S
In the present paper we study the time evolution of power spectra
of galactic cosmic ray fluctuations during the last three solar
cycles (1968-2002) using data of 5-min count rates from two far
spaced high-latitude neutron monitors, Tixie Bay (Russia) and Oulu
(Finland). We have shown that the power spectrum of cosmic ray
fluctuations is a sub ject of a regular long-term periodic 11-year
modulation in phase with solar activity, in accordance with variations
of the inertial part of the interplanetary magnetic field turbulence
power spectrum. These results present a new kind of modulation of
cosmic ray intensities.
Title: Active longitudes in sunspot activity: Century scale
persistence
Authors: Berdyugina, S. V.; Usoskin, I. G.
Bibcode: 2003A&A...405.1121B
Altcode:
A novel analysis of sunspot group data for the past 120 years reveals
that sunspots in both northern and southern hemispheres are formed
preferably in two persistent active longitudes separated by 180°. In
the Carrington reference frame, the active longitudes continuously
migrate in phase with respect to the Carrington meridian with a variable
rate. They remain however a quasi-rigid structure. We find that the
migration of the active longitudes is determined by changes of the mean
latitude of sunspots and the differential rotation. The differential
rotation rate calculated from the migration is in agreement with
SOHO/MDI measurements. The two active longitude periodically alternate
being the dominant region, similar to the ``flip-flop'' phenomenon
known in starspot activity. The period of the oscillations is 3.8
and 3.65 years in the north and south, respectively. The difference
between the periods is significant and can be related to the known
north-south asymmetry in the solar magnetic activity. Our results
provide new observational constraints for current solar dynamo models
and strengthen the solar paradigm for magnetic activity on cool stars.
Title: REal-time COsmic Ray Database (RECORD)
Authors: Usoskin, I.; Kozlov, Valery; Ksenofontov, Leonid, Kudela,
Karel; Starodubtsev, Sergei; Turpanov, Alexey; Yanke, Victor
Bibcode: 2003ICRC....6.3473K
Altcode: 2003ICRC...28.3473K; 2003ICRC....6.3473U
In this paper we present a first distributed REal-time COsmic Ray
Database (RECORD). The aim of the project is to develop a unified
database with data from different neutron monitors collected together,
in unified format and to provide a user with several commonly
used data access methods. The database contains not only original
cosmic ray data but also auxiliary data necessary for scientific data
analysis. Currently the database includes Lomn.Stit, Moscow, Oulu; Tixie
Bay, Yakutsk stations. The main database server is located in IKFIA SB
RAS (Yakutsk) but there will be several mirrors of the database. The
database and all its mirrors are up dated on the nearly real-time
(1 hour) basis. The data access software includes WWW-interface, Perl
scripts and C library, which may be linked to a user program. Most of
frequently used functions are implemented to make it operable to users
without SQL language knowledge. A draft of the data representation
standard is suggested, based on common practice of neutron monitor
community. The database engine is freely distributed open-sourced
PostgreSQL server coupled with a set of replication to ols developed
at Bio engineering division of the IRCCS E.Medea, Italy.
Title: Long-Term Cosmic Ray Intensities: Physical Reconstruction
Authors: Usoskin, I. G.; Mursula, K.; Solanki, S. K.; Schuessler,
M.; Kovaltsov, G. A.
Bibcode: 2003ICRC....7.4041U
Altcode: 2003ICRC...28.4041U
Solanki et al. (2000) have recently calculated the open solar magnetic
flux for the last 400 years from sunspot data. Using this reconstructed
magnetic flux as an input to a simple spherically symmetric quasi-steady
state model of the heliosphere, we calculate the expected differential
spectra and integral intensity of galactic cosmic rays at the Earth's
orbit since 1610. The calculated cosmic ray integral intensity is in
good agreement with the neutron monitor measurements during the last
50 years. Moreover, using the specific yield function of cosmogenic
10 Be radionuclide production in the atmosphere, we also calculate
the expected 10 Be production rate which exhibits an excellent
agreement with the actual 10 Be abundance in polar ice over the
last 400 years. Here we present a physical model for the long-term
reconstruction of cosmic ray intensity at 1 AU. The reconstruction
is based on a combination of the solar magnetic flux model and a
heliospheric model. This model allows us to calculate the expected
intensity of galactic cosmic rays (GCR) at the Earth's orbit for the
last 400 years. Details can be found in [25]. Using the numerical recip
e of Solanki et al. [21] and the group sunspot number series (Fig. 1.a)
[11] we have calculated the open solar magnetic flux Fo since 1610 as
shown in Fig. 1.b. In order to calculate galactic cosmic ray (GCR)
spectra we use a spherically symmetric quasi-steady sto chastic
simulation model described in detail elsewhere [24], which reliably
describes the long-term GCR modulation during the last 50 years. In this
model, the most important parameter of the heliospheric modulation of
GCR is the modulation strength [10]: Φ = (D - rE )V /(3κo), where D
= 100 AU is the heliospheric boundary and rE = 1 AU, V = 400 km/s is
the constant solar wind velocity and κo is the rigidity indep endent
part of the diffusion coefficient. Thus, all changes in the modulation
strength Φ in our model are related to the changing diffusion
Title: Long-Term Cosmic Ray Modulation by Heliospheric Parameters:
Non-linear Relations
Authors: Usoskin, I. G.; Kovaltsov, G. A.; Mursula, K.; Alkano, K.
Bibcode: 2003ICRC....7.3803U
Altcode: 2003ICRC...28.3803U
The heliospheric modulation strength is a good parameter for the
long-term modulation of cosmic rays in the neutron monitor energy
range. Here we study an empirical relation between the modulation
strength and the global heliospheric parameters: the heliospheric
current sheet tilt angle, the open solar magnetic flux and the global
IMF polarity. The suggested relation closely repro duces the measured
annual NM count rates. Using the measured IMF parameters and the
modulation strength values computed since 1951, this relation allows
us to reconstruct the annual tilt angle for about 25 years before
the time of direct measurements of the tilt angle. In addition to more
sophisticated theoretical models of galactic cosmic ray (GCR) modulation
it is also useful to study empirical regression models. Usually
such models linearly relate various heliospheric parameters to the
GCR intensity at a fixed energy (see, e.g., [2]). Here we try to
generalize this approach. A general parameter of the heliospheric
modulation of GCR is the modulation strength Φ, which defines the
shape of the modulated GCR spectrum for many practical purposes. E.g.,
for a given value of Φ one can calculate an approximate shape of GCR
differential energy spectrum and the expected count rate of a cosmic
ray detector [1], [11]. The modulation strength is measured in MV,
has the physical meaning of the average rigidity loss of CR particles
in the heliosphere and takes the following form [4] Φ = (D - rE )V
/(3κo ), where D is the distance of heliospheric boundary (termination
shock), rE = 1 AU, V is the solar wind velocity and κo is the (rigidity
indep endent part of the) GCR diffusion coefficient. Although defined
only in 1D, Φ can also be used in the real conditions as a formal
parameter that fits GCR spectra calculated in 1D model to the actual
GCR spectrum measured at 1 AU. The values of Φ have been calculated
for the last 50 years [11]. However, here we use an up dated Φ series
(Fig. 1.a) where heavier species of GCR (α-particles) are also taken
into account. The value of Φ depends on several global heliospheric
parameters as discussed below. In con-
Title: The lost sunspot cycle: Reanalysis of sunspot statistics
Authors: Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2003A&A...403..743U
Altcode:
We have recently suggested that one low sunspot cycle was possibly lost
in 1790s (Usoskin et al. 2001, A&A, 370, L31). In this paper we
present the results of a rigorous statistical analysis of all available
sunspot observations around the suggested additional cycle minimum in
1792-1793. First we estimate the uncertainty of a monthly mean sunspot
number reconstructed from a single daily observation. Then we compare,
using quantitative statistical tests, the average level of sunspot
activity in 1792-1793 with the average activity during the minimum,
mid-declining and maximum phases of cycles in the well-measured
reference period 1850-1996. We show that, contrary to the results by
Krivova et al. (2002), the level of sunspot activity in 1792-1793 is
statistically similar to that in the minimum phase, and significantly
different from that in the mid-declining and maximum phases. Using the
estimated uncertainties, we also calculate new, weighted annual values
of Rg in 1790-1796 which show a clear minimum in 1792-1793
and a maximum in 1794-1795, supporting the idea of an additional weak
cycle in 1790's.
Title: Reconstructing the long-term cosmic ray intensity: linear
relations do not work
Authors: Mursula, K.; Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2003AnGeo..21..863M
Altcode:
It was recently suggested (Lockwood, 2001) that the cosmic ray intensity
in the neutron monitor energy range is linearly related to the coronal
source flux, and can be reconstructed for the last 130 years using the
long-term coronal flux estimated earlier. Moreover, Lockwood (2001)
reconstructed the coronal flux for the last 500 years using a similar
linear relation between the flux and the concentration of cosmogenic
10 Be isotopes in polar ice. Here we show that the applied linear
relations are oversimplified and lead to unphysical results on long
time scales. In particular, the cosmic ray intensity reconstructed
by Lockwood (2001) for the last 130 years has a steep trend which is
considerably larger than the trend estimated from observations during
the last 65 years. Accordingly, the reconstructed cosmic ray intensity
reaches or even exceeds the local interstellar cosmic ray flux around
1900. We argue that these unphysical results obtained when using
linear relations are due to the oversimplified approach which does
not take into account the complex and essentially nonlinear nature of
long-term cosmic ray modulation in the heliosphere. We also compare
the long-term cosmic ray intensity based on a linear treatment with
the reconstruction based on a recent physical model which predicts a
considerably lower cosmic ray intensity around 1900.
Title: The lost sunspot cycle: Reanalyzing the sunspot statistics
Authors: Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2003EAEJA.....8819U
Altcode:
It has been recently suggested that one sunspot cycle was possibly lost
in 1790s (Usoskin et al., 2001, A&A, 370, L31). Here we present
results of a rigorous statistical analysis of all available sunspot
observations around 1792-1793, when the additional cycle minimum was
suggested to occur. First we estimate the uncertainty of a monthly
sunspot number mean which consists of a single daily observation. Then
we compare, using quantitative statistical tests, the pattern of sunspot
activity in 1792-1793 and during the minimum, mid-declining and maximum
phases of well-measured cycles in the reference period of 1850-1996. We
show that the pattern of sunspot activity in 1792-1793 is statistically
similar to that in the minimum phase, and significantly different
from that in the mid-declining and maximum phases. We calculate the
weighted annual values of R_g in 1790-1796 which clearly show a small
cycle starting in 1793 and reaching its maximum in 1795. We discuss
that the possible existence of a new cycle does not contradict to the
indirect proxies of solar activity (e.g., cosmogenic isotope data). We
also discuss the implications of the new cycle for solar activity,
in particular for the cycle length distribution, the Gnevyshev-Ohl
rule and the Waldmeier relation between the cycle amplitude and the
length of the ascending and descending phase.
Title: Lost sunspot cycle in the beginning of Dalton minimum: New
evidence and consequences
Authors: Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2002GeoRL..29.2183U
Altcode: 2002GeoRL..29x..36U
We have recently suggested that one solar cycle was lost in the
beginning of the Dalton minimum during 1790s [Usoskin et al.,
2001]. Earlier, this cycle has been combined with the preceding
activity to form the exceptionally long solar cycle 4 in 1784-1799
with an irregular phase evolution. Here we show that historical data
of auroral occurrence provide independent evidence for the existence
of the new cycle. Using a heliospheric model we demonstrate that
10Be or any other cosmogenic isotope data do not exclude
the possibility of a new cycle. We also discuss the other implications
of the new cycle for solar activity, in particular the cycle length
distribution and the Waldmeier relation between the cycle amplitude
and the length of the ascending and descending phase. Including the
new cycle also restores the Gnevyshev-Ohl rule of cycle pairing and
removes the phase catastrophe in the beginning of the Dalton minimum.
Title: Simulating regularity and randomness in sunspot activity
Authors: Usoskin, I. G.; Mursala, K.; Kovaltsov, G. A.
Bibcode: 2002ESASP.506..863U
Altcode: 2002svco.conf..863U; 2002ESPM...10..863U
The time series of sunspot activity displays both regular features
and randomness, and their interrelation has been studied during last
decades. We present here a model of sunspot production which employs
three components of solar magnetic field: the 22-year dynamo field, a
weak constant relic field, and a randomly fluctuating field. Within this
model, sunspots are produced when the total field exceeds the buoyancy
threshold. This model can reproduce the main features of sunspot
activity throughout the 400-year period of direct solar observations,
including two different sunspot activity modes, the present, normal
sunspot activity and the Maunder minimum. The two sunspot activity
modes could be modeled by only changing the level of the dynamo field
while keeping the other two components constant. We discuss the role
of the three components and how their relative importance changes
between normal activity and great minimum times. We found that the
relic field must be about few per cent of the dynamo field in normal
activity times. Also, we find that the dynamo field during the Maunder
minimum was small but non-zero, being suppressed typically by an order
of magnitude with respect to its value during normal activity times.
Title: A physical reconstruction of cosmic ray intensity since 1610
Authors: Usoskin, Ilya G.; Mursula, Kalevi; Solanki, Sami K.;
Schüssler, Manfred; Kovaltsov, Gennady A.
Bibcode: 2002JGRA..107.1374U
Altcode:
The open solar magnetic flux has been recently reconstructed by [2000,
2002] for the last 400 years from sunspot data. Using this reconstructed
magnetic flux as an input to a spherically symmetric quasi-steady
state model of the heliosphere, we calculate the expected intensity
of galactic cosmic rays at the Earth's orbit since 1610. This new,
physical reconstruction of the long-term cosmic ray intensity is
in good agreement with the neutron monitor measurements during the
last 50 years. Moreover, it resolves the problems related to previous
reconstruction for the last 140 years based on linear correlations. We
also calculate the flux of 2 GeV galactic protons and compare it to
the cosmogenic 10Be level in polar ice in Greenland and
Antarctica. An excellent agreement between the calculated and measured
levels is found over the last 400 years.
Title: Heliospheric modulation strength during the neutron monitor era
Authors: Usoskin, I. G.; Alanko, K.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2002SoPh..207..389U
Altcode:
Using a stochastic simulation of a one-dimensional heliosphere we
calculate galactic cosmic ray spectra at the Earth's orbit for different
values of the heliospheric modulation strength Φ. Convoluting these
spectra with the specific yield function of a neutron monitor, we
obtain the expected neutron monitor count rates for different values
of Φ. Finally, inverting this relation, we calculate the modulation
strength using the actually recorded neutron monitor count rates. We
present the reconstructed annual heliospheric modulation strengths for
the neutron monitor era (1953-2000) using several neutron monitors from
different latitudes, covering a large range of geomagnetic rigidity
cutoffs from polar to equatorial regions. The estimated modulation
strengths are shown to be in good agreement with the corresponding
estimates reported earlier for some years.
Title: Long-term cosmic ray intensity vs. solar proxies: a simple
linear relation does not work
Authors: Mursula, K.; Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2002ESASP.477..463M
Altcode: 2002scsw.conf..463M
It was recently suggested (Lockwood et al., 2000; 2001) that the cosmic
ray intensity in the neutron monitor energy range is linearly related
to coronal source flux, and can be reconstructed for 130 years using
the estimated long term coronal flux. Moreover, by reversing this
relation, they reconstructed the coornal flux on the 500-year scale
using the cosmogenic 10Be data as an index of cosmic ray
intensity. Here we show that a linear regression is oversimplified
and leads to unphysical results on long time scales. In particular,
the reconstructed cosmic ray intensity has a steep trend which is four
times larger than the allowed upper bound. The reconstructed cosmic
ray intensity exceeds the local interstellar cosmic ray flux around
1900. We argue that the unphysical results using a linear assumption
are due to the oversimplified approach which does not account for
complexity and significant nonlinearity of cosmic ray modulation in
the heliosphere. We show also that there is no homogeneous linear
relation between coronal source flux and cosmic rays.
Title: The start of the Dalton minimum: Was one sunspot cycle lost
in late XVIII century?
Authors: Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2002ESASP.477..257U
Altcode: 2002scsw.conf..257U
We have recently suggested that one solar cycle was lost in the
beginning of the Dalton minimum because of sparse and partly unreliable
sunspot observations during 1790s (Usoskin et al. 2001). So far
this cycle has been combined with the preceding activity to form the
exceptionally long solar cycle #4 in 1784 - 1799 which has an irregular
phase evolution (known as the phase catastrophe) and other problems
discussed in earlier literature. Based on a re-analysis of available
sunspot data, we have suggested that solar cycle #4 is in fact a
superposition of two cycles: a normal cycle in 1784 - 1793 ending at
the start of the Dalton minimum, and a new weak cycle in 1793 - 1800
which was the first cycle within the Dalton minimum. Including the new
cycle resolves the phase catastrophe and leads to a consistent view
of sunspot activity around the Dalton minimum. It also restores the
Gnevyshev-Ohl rule of cycle pairing across the Dalton minimum. Here
we summarize these findings and show that the existence of a new cycle
is supported by the auroral occurrence in Europe in late XVIII century.
Title: A 22-year cycle in sunspot activity
Authors: Mursula, K.; Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2002AdSpR..29.1979M
Altcode:
We study the recently presented group sunspot number series and show
that a persistent 22-year periodicity exists in sunspot activity
throughout the entire period of about 400 years of direct sunspot
observations. The amplitude of this periodicity in total cycle intensity
is about 20% of the present intensity level. A 22-year periodicity
in sunspot activity is naturally produced by the 22-year magnetic
dynamo cycle in the presence of a relic magnetic field. Accordingly,
a persistent 22-year periodicity in sunspot activity gives strong
evidence for the existence of such a relic magnetic field in the
Sun. The stable phase and the roughly constant amplitude of this
periodicity during times of very different sunspot activity level
strongly support this interpretation.
Title: Heliospheric Modulation Strength During The Neutron Monitor Era
Authors: Usoskin, I. G.; Alanko, K.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2002EGSGA..27.3884U
Altcode:
Using a stochastic simulation of a one-dimensional heliosphere we
calculate galactic cosmic ray spectra at the Earth's orbit for different
values of the heliospheric mod- ulation strength. Convoluting these
spectra with the specific yield function of a neu- tron monitor, we
obtain the expected neutron monitor count rates for different values of
the modulation strength. Finally, inverting this relation, we calculate
the modula- tion strength using the actually recorded neutron monitor
count rates. We present the reconstructed annual heliospheric modulation
strengths for the neutron monitor era (19532000) using several
neutron monitors from different latitudes, covering a large range of
geomagnetic rigidity cutoffs from polar to equatorial regions. The
estimated modulation strengths are shown to be in good agreement with
the corresponding esti- mates reported earlier for some years.
Title: Missed sunspot cycle in late XVIII century: new evidences
Authors: Usoskin, I.; Mursula, K.; Nevanlinna, H.; Kovaltsov, G.
Bibcode: 2002cosp...34E.862U
Altcode: 2002cosp.meetE.862U
We suggest that one solar cycle was lost in the beginning of the
Dalton minimum because of sparse and partly unreliable sunspot
observations during 1790s. So far this cycle has been combined
with the preceding activity to form the exceptionally long solar
cycle #4 in 1784-1799 which has an irregular phase evolution (known
as the phase catastrophe) and other problems discussed in earlier
literature. Based on a reanalysis of available sunspot data, we have
suggested that solar cycle #4 is in fact a superposition of two cycles:
a normal cycle in 1784-1793 ending at the start of the Dalton minimum,
and a new weak cycle in 1793-1800 which was the first cycle within the
Dalton minimum. Including the new cycle resolves the phase catastrophe
and leads to a consistent view of sunspot activity around the Dalton
minimum. It also restores the Gnevyshev-Ohl rule of cycle pairing across
the Daltom nimimum. Here we summarize these findings and present new
independent geomagnetic evidences favouring the existence of a new
cycle in late XVIII century. We also show that the available data
of cosmogenic isotopes 10 B e and 14 C cannot serve as a test of the
existence of the new cycle.
Title: Heliospheric modulation strength during the neutron monitor era
Authors: Usoskin, I.; Alanko, K.; Mursula, K.; Kovaltsov, G.
Bibcode: 2002cosp...34E.868U
Altcode: 2002cosp.meetE.868U
The heliospheric modulation strengthis an important quantitative
measure of the efficiency of heliospheric modulation of cosmic rays,
however, it is not easy to estimate it in practice. Here we suggest a
physical estimate of the modulation strength on yearly time scale from
data of the neutron monitor network. Using a stochastic simulation
of a one-dimensional heliosphere we calculate galactic cosmic ray
spectra at the Earth's orbit for different values of the heliospheric
modulation strength . Convoluting these spectra with the specific
yield function of a neutron monitor, we obtain the expected neutron
monitor count rates for different values of . Finally, inverting this
relation, we calculate the modulation strength using the actually
recorded neutron monitor count rates. We present the reconstructed
annual heliospheric modulation strengths for the neutron monitor era
(1951-2000) using several neutron monitors from different latitudes,
covering a large range of geomagnetic rigidity cutoffs from polar to
equatorial regions. The estimated modulation strengths are shown to
be consistent among different neutron monitors and in good agreement
with the corresponding estimates reported earlier for some years.
Title: Physical reconstruction of the long-term heliospheric
modulation of cosmic rays
Authors: Usoskin, I.; Mursula, K.; Solanki, S.; Shuessler, M.;
Kovaltsov, G.
Bibcode: 2002cosp...34E.902U
Altcode: 2002cosp.meetE.902U
Open solar magnetic flux has been recently reconstructed by Solanki
et al. (2000, 2002) for the last 400 years from sunspot data. Using
this reconstructed magnetic flux as an input to a spherically symmetric
quasi-steady state model of the heliosphere, we calculate the expected
intensity of galactic cosmic rays at the Earth's orbit since 1610. This
calculated cosmic ray intensity is in good agreement with the neutron
monitor measurements during the last 50 years. Moreover, we calculate
the flux of 2 GeV galactic protons and compare it to the cosmogenic
10 B e level in polar ice in Greenland and Antarctica. An excellent
agreement between the calculated and actual levels is found over the
last 400 years.
Title: Long-term Cosmic Ray Intensity Vs. Solar Proxies: A Simple
Linear Relation Does Not Work
Authors: Mursula, K.; Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2002EGSGA..27.3882M
Altcode:
It was recently suggested (Lockwood et al., 2000; 2001) that the cosmic
ray intensity in the neutron monitor energy range is linearly related
to coronal source flux, and can be reconstructed for 130 years using the
estimated long term coronal flux. Moreover, by reversing this relation,
they reconstructed the coronal flux on the 500-year scale us- ing
the cosmogenic 10Be data as an index of cosmic ray intensity. Here we
show that a linear regression is oversimplified and leads to unphysical
results on long time scales. In particular, the reconstructed cosmic ray
intensity has a steep trend which is four times larger than the allowed
upper bound. The reconstructed cosmic ray intensity ex- ceeds the local
interstellar cosmic ray flux around 1900. We argue that the unphysical
results using a linear assumption are due to the oversimplified approach
which does not account for complexity and significant nonlinearity of
cosmic ray modulation in the heliosphere. We show also that there is no
homogeneous linear relation between coronal source flux and cosmic rays.
Title: Was One Sunspot Cycle Lost In Late Xviii Century?
Authors: Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2002EGSGA..27.3897U
Altcode:
We suggest that one solar cycle was lost in the beginning of the Dalton
minimum because of sparse and partly unreliable sunspot observations
during 1790s. So far this cycle has been combined with the preceding
activity to form the exceptionally long solar cycle #4 in 17841799
which has an irregular phase evolution (known as the phase catastrophe)
and other problems discussed in earlier literature. Based on a re-
analysis of available sunspot data, we have suggested that solar
cycle #4 is in fact a superposition of two cycles: a normal cycle
in 17841793 ending at the start of the Dalton minimum, and a new
weak cycle in 17931800 which was the first cycle within the Dalton
minimum. Including the new cycle resolves the phase catastrophe and
leads to a consistent view of sunspot activity around the Dalton
minimum. It also restores the Gnevyshev-Ohl rule of cycle pairing
across the Daltom nimimum. Here we summarize these findings and show
that the existence of a new cycle is supported by the auroral occurrence
in Europe in late XVIII century.
Title: Reconstruction of Cosmic Ray Intensity Since 1610
Authors: Usoskin, I. G.; Mursula, K.; Solanki, S. K.; Schüssler,
M.; Kovaltsov, G. A.
Bibcode: 2002EGSGA..27.5173U
Altcode:
Open solar magnetic flux has been recently reconstructed by Solanki
et al. (2000, 2002) for the last 400 years from sunspot data. Using
this reconstructed magnetic flux as an input to a spherically symmetric
quasi-steady state model of the heliosphere, we calculate the expected
intensity of galactic cosmic rays at the Earth's orbit since 1610. This
calculated cosmic ray intensity is in good agreement with the neutron
monitor measurements during the last 50 years. Moreover, we calculate
the flux of 2 GeV galactic protons and compare it to the cosmogenic
10Be level in polar ice in Greenland and Antarctica. An excellent
agreement between the calculated and actual levels is found over the
last 400 years.
Title: Persistent active longitudes in sunspot activity
Authors: Berdyugina, S.; Usoskin, I.
Bibcode: 2002cosp...34E.864B
Altcode: 2002cosp.meetE.864B
It has been recently shown that spot activity of cool stars
including solar analogues, is grouped in two clearly distinguished
active longitudes which are persistent within at least one starspot
cycle. Solar data including positional information of individual
sunspots / groups extends back for about 130 years covering 12 solar
cycles. Here we present the results of our research of longitudinal
distribution of sunspot activity using an analysis similar to
that applied to the stars. First, we synthesized, from the actual
sunspot data, the sun's light curve as if it was defined only by
spots. Then solar images were calculated from this light curve, giving
a natural smoothing of the spot pattern. For each Carrington rotation,
longitudinal position of these smoothed spot regions was calculated. The
analysis reveals the following main features: - Sunspot activity
is grouped in two active longitudes (with the differential rotation
taken into account) 180o apart from each other which are persistent
through the entire studied period of 12 cycles, similarly to stars. -
The longitude migration is determined by changing the mean latitude of
sunspot activity (the Maunder butterfly) and differential rotation. -
The two longitudes periodically alternate the dominant activity with
about 3.7 year period implying for the existence of the Sflip-flopT
phenomenon known in - starspot activity.
Title: Physical reconstruction of long-term solar activity
Authors: Usoskin, I.; Solanki, S.; Schuessler, M.; Mursula, K.;
Kovaltsov, G.
Bibcode: 2002cosp...34E.901U
Altcode: 2002cosp.meetE.901U
For many applications in dynamo theory and solar-terrestrial research
it is important to know the evolution of solar activity on long time
scales (centuries to millennia). Previous reconstructions were based
upon either multi-harmonic backward extrapolation of the known sunspot
records or on the assumption of a linear relation between terrestrial
proxies (e.g., cosmogenic isotope abundance) and solar activity. Here
we present, for the first time, a physical reconstruction of sunspot
activity on long time scales from the cosmogenic 10 Be records. We
use a numerical inversion of a combined physical solar-heliospheric
model (Usoskin et al., 2002), which is essentially non-linear. Using
physical rather than empirical relations on all steps, we present a
reconstruction of sunspot activity since the 15th century. Uncertainties
of the reconstruction are discussed in details. It is important that
the current high level of sunspot activity is unique on the millennium
time scale.
Title: Direct penetration of anisotropic solar proton flux through
the postnoon magnetopause: evidence of magnetosphere anomaly?
Authors: Vashenyuk, E.; Gvozdevsky, B.; Pchelkin, V.; Usoskin, I.;
Mursula, K.; Kovaltsov, G.
Bibcode: 2002cosp...34E2095V
Altcode: 2002cosp.meetE2095V
Count rates of two closely located neutron monitors (NMs) at Oulu and
Apatitysometimes depicted an unusually different behavior during an
anisotropic onsetphase of a number of ground level enhancements (GLEs)
caused by relativisticsolar cosmic rays. Of 24 years of observations
( 27 GLE) there were revealed 4 suchcases. In all of them the NM with
a higher count rate (Oulu on 2 May 1998 and 15April 2001, Apatity on
23 September, 1978 and 14 July 2000) was located in the so-called 14
MLT region (14-16 hours of Magnetic Local Time) known as location
ofintense field aligned currents, dayside auroras etc. At the same
time the calculatedasymptotic cones of Apatity and Oulu stations
were "looking" under the large angleto an IMF direction and in any
way could not accept an anisotropic solar proton fluxpropagating
along the IMF. Nevertheless one of the station pair which was
locatedinside the 14-16 MLT sector showed an excess in count rate due to
anisotropicfraction of solar proton flux. Together with the Apatity and
Oulu NMs data ouranalysis comprised also the data on the worldwide NM
network as well ascomputation of their asymptotic cones These were done
by means of trajectorycalculations in the up -to date magneto pheric
models of Tsyganenko 1989 and 1996.sOn the basis of observed data we
can assume, that the cause of marked unusualdifference between Apatity
and Oulu GLE effect can be the not discounted anomalyin the afternoon
magnetosphere. .It can be connected, for example to the structure
ofnagnetospheric cleft. The noted here effect specifies necessity of
additional study ofmagnetosphere structure in the afternoon sector
that may be a subject to occurringhere intensive geophysical processes.
Title: Nitrate abundance in polar ice during the great solar activity
minimum
Authors: Gladysheva, O. G.; Kocharov, G. E.; Kovaltsov, G. A.; Usoskin,
I. G.
Bibcode: 2002AdSpR..29.1707G
Altcode:
In the present paper we study variations of the nitrate content in
Greenland ice core for the last 400 years. These data were obtained by
high-precision measurements performed by the University of Kansas. It
is shown that approximately 20-year periodicity dominates in the
nitrate series during the Maunder minimum (1645-1715) due to similar
variations of galactic cosmic ray intensity. During times of normal
high solar activity level, the 4-6-year periodicity dominates in the
nitrate series. This is probably due to a superposition of fluxes of
galactic and solar cosmic rays, and due to the creation of favourable
conditions for the nitrate precipitation.
Title: Evidence for charge drift modulation at intermediate solar
activity from the flux variation of protons and α particles
Authors: Boella, G.; Gervasi, M.; Mariani, S.; Rancoita, P. G.;
Usoskin, I. G.
Bibcode: 2001JGR...10629355B
Altcode:
We have studied the flux of galactic protons and helium nuclei measured
at 1 AU along two consecutive solar activity cycles. We have correlated
cosmic ray fluxes measured on IMP 8 satellite at low energy (50-300
MeV amu-1) with neutron monitor counts registered at Climax
station (at energies above few GeV) during the period 1973-1995. We have
found a systematic excess in the flux of the positive charged particles
during the periods with positive solar magnetic field polarity (A>0)
with respect to the flux during the periods of negative polarity
(A<0). This flux excess gives an experimental evidence that charge
drift effect plays an important role in the modulation of galactic
cosmic rays. A systematic investigation of charge drift modulation is
presented. The dependence of the drift effect on the solar activity
phase and the particle energy has been also studied. A variation of
the proton (as well as helium) flux might be as large as 40%, at the
solar activity minimum of two contiguous cycles, at energy <=100 MeV.
Title: Nitrate abundance in polar snow during last 50 year: connection
to atmospheric ionization
Authors: Gladysheva, O. G.; Dmitriev, P. B.; Usoskin, I. G.; Barkov,
N. I.; Ekaykin, A. A.; Nikanorov, V. V.
Bibcode: 2001ICRC...10.4191G
Altcode: 2001ICRC...27.4191G
A few yearly series of the nitrate abundance in polar snow are
studied. One of them has been measured in the snow samples collected
in a pit dug at russian Vostok Station (East Antarctic). The other
series has been obtained in Antarctic and Greenland. The studied time
interval covers the last 50 years. These series are influenced by
different local terrestrial drivers while the extraterrestrial force
is similar. The nitrate series are analysed along with calculations of
the cosmic ray induced ionisation of the upper atmosphere. A relative
role of extraterrestrial factors, in particular of strong solar proton
events, is discussed.
Title: The MUG experiment for observing muon fluxes underground:
test data and development plans
Authors: Elo, A. -M.; Jaemsen, T.; Kangas, J.; Mursula, K.; Peltoniemi,
J.; Usoskin, I. G.; Vallinkoski, M.; Valtonen, E.
Bibcode: 2001ICRC....3.1249E
Altcode: 2001ICRC...27.1249E
A new multilevel Muons UnderGround experiment (MUG) for observing
muon fluxes underground is located in the Pyh¨asalmi zinc mine in
Central Finland. The detectors consist of vertically overlapping plastic
scintillator pairs. Three scintillator pairs are situated on the ground
level. Six pairs are 90 metres un-derground and another six pairs
are 210 metres underground. The counting rates of coincident pulses
in scintillator pairs are recorded in the preliminary phase of the
experiment. In this paper we study the test data obtained with the MUG
instruments in order to check the acceptability of their operation. One
purpose of the MUG experiment is to investigate the suitability of
the Pyhasalmi mine as a location for scientific experiments. The test
data are also examined in this respect. Development plans for the MUG
experiment are also outlined in this paper.
Title: Geomagnetic cutoff Penumbra structure: approach by
transmissivity function
Authors: Bobik, P.; Kudela, K.; Usoskin, I.
Bibcode: 2001ICRC...10.4056B
Altcode: 2001ICRC...27.4056B
Numerical tracing of cosmic ray trajectories in the model magnetospheric
field is widely used to understand the "magnetospheric optics" of the
Earth's magnetosphere for primary cosmic rays and their access to ground
based observation sites. Recent review on the subject can be found,
e.g. in (Smart et al., 2000). Penumbra structure is usually described
as a system of allowed and forbidden trajectories (A,F) between low,
RL , and upper, RU , cutoff rigidities. The probability of a particle
in a given rigidity interval within (RL,RU) to access the position of a
cosmic ray station, the transmissivity function TF, is deduced from the
(A,F) structure which is dependent on the elementary step in rigidity
for computations, on local time (if the external field is included) and
on the geomagnetic activity level. We study TF using Tsyganenko'89 field
model with rigidity steps ∼R=10-5 GV - 10-1 GV, for the high latitude
Oulu site (65.05o N 25.47o E). We illustrate the penumbra structure
in terms of the divergence of asymptotic direction of neighbouring
allowed trajectories. The TF function weighted statistically by the
Kp distribution over long time may serve as a tool for CR transparency
characteristic at a particular station.
Title: A new multilevel experiment MUG for observing muon fluxes
underground
Authors: Jaemsen, T.; Elo, A. -M.; Kangas, J.; Mursula, K.; Peltoniemi,
J.; Usoskin, I. G.; Vallinkoski, M.; Valtonen, E.
Bibcode: 2001ICRC....3.1250J
Altcode: 2001ICRC...27.1250J
We describe a new Muons UnderGround experiment (MUG) for observing
muon uxes underground. The experiment is situated in the Pyhasalmi
zinc mine in Central Finland. The muon detectors consist of two
vertically overlapping plastic scintillators. Six pairs of detectors
are located 210 metres underground, another six pairs 90 metres
underground, and three pairs are on the ground level. The dimensions
of the scintillators are 50 cm × 50 cm in the horizontal plane
and their thickness is 5 cm. Each scintillator is equipped with a
Hamamatsu R329-02 photomultiplier tube with fast time response. In the
preliminary phase of the experiment the counting rates of coincidences
of the scintillator pairs are recorded. In this paper we describe the
detectors and the experimental setup in more detail.
Title: Heliospheric modulation strength during the neutron monitor
epoch
Authors: Usoskin, I. G.; Alanko, K.; Mursula, K.; Kudela, K.;
Kovaltsov, G. A.
Bibcode: 2001ICRC....9.3810U
Altcode: 2001ICRC...27.3810U
Using a simple stochastic 1D simulation model of the heliosphere we
calculate galactic cosmic ray spectra at the Earth's orbit for different
values of the heliospheric modulation strength Φ. Convoluting these
spectra with the specific yield function of a neutron monitor, we obtain
the expected neutron monitor count rates for different values of Φ. We
present here a normalization method which allows to easily estimate
the value of Φ on the basis of actually recorded neutron monitor
count rates. By means of this approach we estimate the heliospheric
modulation strength for the neutron monitor era using long-term records
of count rates from the high-latitude Oulu and mid-latitude Hermanus
neutron monitors.
Title: The GLE of 14 July 2000: comparative analysis of increase
effect on close neutron monitors in Apatity and Oulu
Authors: Vashenyuk, E. V.; Gvozdevsky, B. B.; Phelkin, V. V.; Usoskin,
I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2001ICRC....8.3383V
Altcode: 2001ICRC...27.3383V
Count rates of two closely located neutron monitors (NMs) at Oulu and
Apatity depicted an unusually different behaviour during the onset
phase of the ground- level enhancement (GLE) of 14 July 2000. Similar
differences were observed during the onsets of GLEs of 2 May 1998
and 15 April 2001. All these three events took place after a strong
Forbush decrease, implying significantly disturbed interplanetary
and geomagnetic conditions. In all cases the NM with a higher count
rate (Oulu on 2 May 1998 and 15 April 2001, Apatity on 14 July 2000)
was located in the so-called 14 MLT region (1416 hours of Magnetic
Local Time) where the maximum dayside auroral intensity and some
other anomalous geophysical phenomena are located. Here we analyse
these events using data from Apatity, Oulu and some other NMs,
as well as their asymptotic cones calculated using the Tsyganenko
1989 magnetospheric model. We suggest that there is an anomaly in
magnetospheric structure in the 14 MLT sector which facilitates the
penetration of cosmic ray protons from the dayside magnetopause to
the ground.
Title: Heliospheric modulation of cosmic rays and solar activity
during the Maunder minimum
Authors: Usoskin, Ilya G.; Mursula, Kalevi; Kovaltsov, Gennady A.
Bibcode: 2001JGR...10616039U
Altcode:
Modern models and direct cosmic ray experiments deal with heliospheric
modulation of cosmic rays only during the recent times of rather
high overall solar activity level. On the other hand, the question
of cosmic ray modulation during the exceptional conditions of very
quiet heliosphere is important. In the present paper we compare the
variations of cosmic ray intensity with solar and auroral activity
during the Maunder minimum (1645-1715) when the Sun was extremely
quiet. We use the newly presented group sunspot number series as a
measure of early solar activity, the auroral observations in central
Europe as an indicator of transient phenomena in the inner heliosphere,
and the radiocarbon data as a proxy of cosmic ray intensity. We find
that both cosmic ray intensity and auroral activity closely follow
the dominant 22-year cyclicity with sunspot activity during the
Maunder minimum. Moreover, the strict antiphase between the 22-year
variation of cosmic ray intensity and sunspot activity suggests that
the 22-year variation in cosmic ray intensity can be explained by the
diffusion-dominated terms of cosmic ray modulation without significant
drift effects. We also discuss the possible origin of the behavior of
the 10Be data which is different from all other parameters
during the Maunder minimum.
Title: On-Line Database of Cosmic Ray Intensities*
Authors: Usoskin, I. G.; Mursula, K.; Kangas, J.
Bibcode: 2001ICRC....9.3842U
Altcode: 2001ICRC...27.3842U
Cosmic ray measurements in Oulu (65.05 o N, 25.47 o E) started in 1964
with a standard 9-NM-64 neutron monitor. The 9-NM-64 neutron monitor
consists of three independent units, each made of three proportional
gas counters. The local vertical geomagnetic cutoff rigidity is about
0.8 GV. The NM at Oulu is one of the most stable and reliable stations
of the World Neutron Monitor Net-work. We have recently launched a
web service of the Oulu NM data. All data on cosmic ray intensity
as recorded by the Oulu NM since 1964 are available in a searchable
on-line database at the URL: http://cosmicrays.oulu.fi The database
contains 1-min resolution data since 1995, 5min resolution data since
1985, and hourly data since 1964, as well as the full information
about the reliability and stability of the recorded cosmic ray
intensities. Besides, 10-sec uncorrected data are available since 1990
upon special requests. *To the memory of the late NM station manager
Hannu Kananen
Title: Cosmogenic Variations of Nitrate Abundance in Polar Ice
Authors: Gladysheva, O. G.; Kocharov, G. E.; Kovaltsov, G. A.; Usoskin,
I. G.
Bibcode: 2001ICRC...27.....G
Altcode:
Time variations of the nitrate content in Greenland ice core for
the last 400 years are analysed. An approximately 20-year cyclicity
dominates the nitrate series during the Maunder minimum (1645-1715)
due to similar variations of galactic cosmic ray intensity. During
times of normal high solar activity level, the 4-6-year periodicity
dominates the nitrate series. This is probably due to a superposition
of fluxes of galactic and solar cosmic rays, and due to favourable
conditions for the nitrate precipitation.
Title: Odd and even cycles in cosmic rays and solar activity
Authors: Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2001ICRC....9.3791U
Altcode: 2001ICRC...27.3791U
We present here a new method to define the evolution of cosmic ray
and solar activity cycles using the time delayed component method in
a 2D phase space. This method is free from the ambiguousness related
to the exact timing of cosmic ray maxima and minima. We study the
relationship between solar activity and cosmic ray intensity for the
last four 11-year cycles. We confirm that the evolution of cosmic
ray intensity is different for odd and even cycles and show that odd
cosmic ray cycles are longer and have longer autocorrelation lengths
than even cycles. The momentary time lag between cosmic ray intensity
and sunspot activity is about one year for odd cycles and small or
negative for even cycles. This reflects the difference in the cosmic
ray modulation conditions for odd and even cycles and is probably
associated with the influence of drift effects.
Title: Cosmic ray intensity vs. solar indices: Is there a simple
linear relation?
Authors: Mursula, K.; Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2001ICRC....9.3838M
Altcode: 2001ICRC...27.3838M
It was recently suggested by Lockwood et al. (2000, 2001) that the
cosmic ray intensity in the neutron monitor energy range is linearly
related to the coronal source flux, and can be reconstructed for much
earlier times using the estimated long term coronal flux. Here we show
that a linear regression is oversimplified and leads to unphysical
results on long time scales. In particular, the reconstructed cosmic
ray intensity has a steep trend which is four times larger than the
allowed upper bound. The reconstructed cosmic ray intensity exceeds
the local interstellar cosmic ray flux around 1900. Also, the 11-year
cycle minimum of the reconstructed cosmic ray intensity in early
1900s is higher than the highest measured maximum in 1965. We argue
that the unphysical results using a linear assumption are due to the
oversimplified approach which does not account for complexity and
significant nonlinearity of CR modulation in the heliosphere.
Title: Was one sunspot cycle lost in late XVIII century?
Authors: Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2001A&A...370L..31U
Altcode:
We suggest that one solar cycle was lost in the beginning of the Dalton
minimum because of sparse and partly unreliable sunspot observations. So
far this cycle was combined with the preceding activity to form the
exceptionally long solar cycle #4 in 1784-1799, leading to an irregular
phase evolution of sunspot activity (known as a phase catastrophe) and
other problems. We reanalyze the available group sunspot numbers and
suggest that solar cycle #4 was in fact a superposition of two cycles: a
normal cycle in 1784-1793 ending at the start of the Dalton minimum and
a new weak cycle in 1793-1800 which was the first full cycle within the
Dalton minimum. Including the new cycle resolves the problems mentioned
above and leads to a consistent view of sunspot activity around the
Dalton minimum. Moreover, it will restore the Gnevyshev-Ohl rule of
cycle pairing throughout the 400-year interval of sunspot observations.
Title: Cosmic Ray Intensity vs. Solar Coronal Source Flux: Is There
a Simple Relation?
Authors: Usoskin, I.; Mursula, K.
Bibcode: 2001AGUSM..SH52A03U
Altcode:
It was recently suggested by Lockwood [2001] that cosmic ray (CR) flux
in the neutron monitor (NM) energy range is directly related to the
solar coronal source flux, and can be reconstructed in the past. Here
we show that this approach is oversimplified and can not be applied
to CR reconstruction in the past. We reanalyse the reconstructed CR
flux comparing it with the observed (Climax) NM flux during the last
four solar cycles. While the details of CR time profile are reasonably
reproduced by the Lockwood's regression model, the overall trend is
questionable. The trend in the Climax NM count rate is about -0.02%
per year while the Lockwood model series gives a much larger trend
of about -0.13% per year. In the observed CR intensity, all maxima
are roughly equally high while the depth of minima varies. However,
in the model series, both maxima and minima are decreasing with time,
leading to an extraneously large trend. This trend also implies a very
high CR flux in early times. E.g., the model CR flux minimum in early
1900s is higher than recent CR maxima, although solar activity maxima
were much higher during that time than present cycle minima. We have
recently estimated the NM response to unmodulated GCR in case of no
heliosphere. This unmodulated Climax NM count rate would be only about
16% higher than the actual count rate in the CR maximum year 1977. On
the other hand, the model Climax NM count rate is 20% higher in the CR
minimum year 1990 than in 1977, thus exceeding the unmodulated CR flux.
Title: Regular and Random Components of Sunspot Activity During
Active Sun and Great Minima: Model Simulation
Authors: Usoskin, I.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2001AGUSM..SH41A22U
Altcode:
We model sunspot production during the two different modes of sunspot
activity (the normal activity level and great minima), using the
idea of a threshold-like mechanism [Ruzmaikin, 1997, 2000]. The model
includes a dynamo field, a constant relic field of the Sun and a random
field. This model describes the main features of sunspot activity both
during normal activity times (dominant 11-year cycle and weak 22-year
cycle) and during the Maunder minimum (sparse sunspot occurrence with
22-year cycle) with the same model parameters, only varying the dynamo
amplitude. The relic field must be about 3-10 % of the dynamo field
in normal activity times.
Title: Simulation of Sunspot Activity During Active Sun and Great
Minima Using Regular, Random and Relic Fields
Authors: Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2001SoPh..199..187U
Altcode:
Developing the idea of Ruzmaikin (1997, 1998), we have constructed a
model of sunspot production using three components of solar magnetic
field: the 22-year dynamo field, a weak constant relic field, and a
random field. This model can reproduce the main features of sunspot
activity throughout the 400-year period of direct solar observations,
including two different sunspot activity modes, the present, normal
sunspot activity and the Maunder minimum. The two sunspot activity
modes could be modeled by only changing the level of the dynamo field
while keeping the other two components constant. We discuss the role of
the three components and how their relative importance changes between
normal activity and great minimum times. We found that the relic field
must be about 3-10% of the dynamo field in normal activity times. Also,
we find that the dynamo field during the Maunder minimum was small
but non-zero, being suppressed typically by an order of magnitude with
respect to its value during normal activity times.
Title: Persistent 22-year cycle in sunspot activity: Evidence for
a relic solar magnetic field
Authors: Mursula, K.; Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2001SoPh..198...51M
Altcode:
We use the recently presented group sunspot number series to show that
a persistent 22-year cyclicity exists in sunspot activity throughout
the entire period of about 400 years of direct sunspot observations. The
amplitude of this cyclicity is about 10% of the present sunspot activity
level. A 22-year cyclicity in sunspot activity is naturally produced
by the 22-year magnetic polarity cycle in the presence of a relic
dipole magnetic field. Accordingly, a persistent 22-year cyclicity in
sunspot activity gives an evidence for the existence of such a relic
magnetic field in the Sun. The stable phase and the roughly constant
amplitude of this cyclicity during times of very different sunspot
activity level strongly support this interpretation.
Title: Dependence of cosmic rays on solar activity for odd and even
solar cycles
Authors: Usoskin, I. G.; Mursula, K.; Kananen, H.; Kovaltsov, G. A.
Bibcode: 2001AdSpR..27..571U
Altcode:
We study the relationship between solar activity and cosmic ray
intensity for the last four full cycles, using the time delayed
component method (Usoskin et al., 1998) in a 2 D phase space. We
present a new method to define the cosmic ray cycle which is free from
ambiguousness related to the exact timing of cosmic ray maxima and
minima. Using this definition, we confirm that the evolution of cosmic
ray intensity is different for odd and even cycles and we show that odd
cosmic ray cycles are longer and have longer autocorrelation interval
lengths than even cycles. The momentary time lag between cosmic ray
intensity and sunspot activity is about one year for odd cycles and
small or negative for even cycles. This reflects the difference in
the cosmic ray modulation conditions for odd and even cycles and is
probably associated with the influence of drift effects.
Title: OULU Neutron Monitor Cosmic Ray Data, January 2000 -
December 2000
Authors: Usoskin, Ilya; Kultima, Johannes
Bibcode: 2001STIN...0253711U
Altcode:
This report presents data on cosmic ray intensities recorded by the
Oulu Cosmic Ray station (Oulu NM) during the year 2000. The data
include pressure corrected hourly count rate of the Oulu NM. The data
are presented in the form of digital tables as well as plots, for each
month separately.
Title: Sensitivity of a neutron monitor to galactic cosmic rays
Authors: Usoskin, I. G.; Bobik, P.; Gladysheva, O. G.; Kananen, H.;
Kovaltsov, G. A.; Kudela, K.
Bibcode: 2001AdSpR..27..565U
Altcode:
We studied the sensitivity of a neutron monitor to Galactic cosmic
rays depending on energy of cosmic ray particles in the interstellar
medium. This is important for studying of the interstellar spectrum
of cosmic rays and details of solar modulation by means of the
world neutron monitor network. We calculated the expected response
of a standard sea-level neutron monitor vs. energy of cosmic ray
particles. First, we studied modulation of a monoenergetic flux
of cosmic rays. Then the specific atmospheric yield function of a
neutron monitor was applied to the calculated flux of cosmic rays at
the Earth's orbit. The obtained response function, being convoluted
with the model interstellar spectrum of cosmic rays, gives a maximum
of neutron monitor sensitivity at around several GV of rigidity of
cosmic ray particles. We performed calculations for weak (φ = 350
MV) and medium (φ = 750 MV) modulation strength. A normalisation of
neutron monitor count rate is suggested which can give an experimental
measure of the overall solar modulation of cosmic rays.
Title: Cyclic behaviour of sunspot activity during the Maunder minimum
Authors: Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2000A&A...354L..33U
Altcode:
We study the behaviour of sunspot activity in 1610-1750, i.e. just
prior to, during and slightly after the Maunder minimum, using the
new series of group sunspot numbers (\cite{hoyt98}). We apply the
delayed component technique and show that, while the transition
from the normal cyclic evolution to the minimum was very abrupt,
the recovery from the minimum was gradual, proceeding through a tiny
but very regular cycle in 1700-1712 and a transition period with a
phase catastrophe in 1712-1720. Exploiting the good coverage of the
Maunder minimum by daily solar observations, we show that the sunspot
ocurrence is concentrated, with a high statistical significance, to
two intervals around 1658 and 1680. Together with the last sunspot
maximum before the Maunder minimum in 1639/1640, and the maximum in
1705, this implies a significant, approximately 22-year periodicity
in sunspot activity during the Maunder minimum.
Title: Persistent 22-year Cycle in Sunspot Activity: Evidence for
a Relic Solar Magnetic Field
Authors: Mursula, K.; Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 2000ESASP.463..387M
Altcode: 2000sctc.proc..387M
No abstract at ADS
Title: Regular and Random Components of Sunspot Activity during
Active Sun and Great Minima: Model Simulation
Authors: Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2000ESASP.463..447U
Altcode: 2000sctc.proc..447U
No abstract at ADS
Title: A 22-year cycle in sunspot activity
Authors: Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2000IAUJD...7E..28U
Altcode:
Recently, using the new group sunspot number series introduced by Hoyt
and Schatten, we have shown that the weak sunspot activity during
the Maunder minimum is modulated by a 22-year periodicity. Here we
demonstrate that, after subtracting the long-term trend due to the
Gleissberg cycle and after averaging the 11-year cyclicity, the group
sunspot series depicts a 22-year cycle with an amplitude of about 10%
of the current sunspot activity level. The well known Gnevyshev-Ohl
rule is a reflection of such a persistent 22-year periodicity. We
discuss the origin of the 22-year cycle in sunspot activity in terms
of a weak relic solar magnetic field.
Title: Regular and random components of sunspot activity: model
simulations
Authors: Usoskin, I. G.; Mursula, K.; Kovaltsov, G. A.
Bibcode: 2000IAUJD...7E..27U
Altcode:
In this contribution we study the question of the relationships between
regularities and chaos in the dynamo mechanism producing sunspot
activity. Following the idea of the threshold-like mechanism of sunspot
production, we considered a simple phenomenological model consisiting
of regular and random-driven components. The model describes pretty well
the main features of the sunspot activity for both normal activity times
(11-year, 22-year cycles, variations of cycle length and amplitude)
and for the Maunder minimum (seemingly sporadic sunspot occurrence).
Title: Protons in near earth orbit
Authors: Alcaraz, J.; Alvisi, D.; Alpat, B.; Ambrosi, G.; Anderhub,
H.; Ao, L.; Arefiev, A.; Azzarello, P.; Babucci, E.; Baldini, L.;
Basile, M.; Barancourt, D.; Barao, F.; Barbier, G.; Barreira, G.;
Battiston, R.; Becker, R.; Becker, U.; Bellagamba, L.; Béné,
P.; Berdugo, J.; Berges, P.; Bertucci, B.; Biland, A.; Bizzaglia,
S.; Blasko, S.; Boella, G.; Boschini, M.; Bourquin, M.; Bruni, G.;
Buenerd, M.; Burger, J. D.; Burger, W. J.; Cai, X. D.; Cavalletti,
R.; Camps, C.; Cannarsa, P.; Capell, M.; Casadei, D.; Casaus, J.;
Castellini, G.; Chang, Y. H.; Chen, H. F.; Chen, H. S.; Chen, Z. G.;
Chernoplekov, N. A.; Chiarini, A.; Chiueh, T. H.; Chuang, Y. L.;
Cindolo, F.; Commichau, V.; Contin, A.; Cotta-Ramusino, A.; Crespo,
P.; Cristinziani, M.; da Cunha, J. P.; Dai, T. S.; Deus, J. D.; Dinu,
N.; Djambazov, L.; D'Antone, I.; Dong, Z. R.; Emonet, P.; Engelberg,
J.; Eppling, F. J.; Eronen, T.; Esposito, G.; Extermann, P.; Favier,
J.; Feng, C. C.; Fiandrini, E.; Finelli, F.; Fisher, P. H.; Flaminio,
R.; Fluegge, G.; Fouque, N.; Galaktionov, Y.; Gervasi, M.; Giusti,
P.; Grandi, D.; Gu, W. Q.; Hangarter, K.; Hasan, A.; Hermel, V.;
Hofer, H.; Huang, M. A.; Hungerford, W.; Ionica, M.; Ionica, R.;
Jongmanns, M.; Karlamaa, K.; Karpinski, W.; Kenney, G.; Kenny, J.;
Kim, W.; Klimentov, A.; Kossakowski, R.; Koutsenko, V.; Laborie, G.;
Laitinen, T.; Lamanna, G.; Laurenti, G.; Lebedev, A.; Lee, S. C.; Levi,
G.; Levtchenko, P.; Liu, C. L.; Liu, H. T.; Lolli, M.; Lopes, I.; Lu,
G.; Lu, Y. S.; Lübelsmeyer, K.; Luckey, D.; Lustermann, W.; Maña,
C.; Margotti, A.; Massera, F.; Mayet, F.; McNeil, R. R.; Meillon, B.;
Menichelli, M.; Mezzanotte, F.; Mezzenga, R.; Mihul, A.; Molinari, G.;
Mourao, A.; Mujunen, A.; Palmonari, F.; Pancaldi, G.; Papi, A.; Park,
I. H.; Pauluzzi, M.; Pauss, F.; Perrin, E.; Pesci, A.; Pevsner, A.;
Pilastrini, R.; Pimenta, M.; Plyaskin, V.; Pojidaev, V.; Postema, H.;
Postolache, V.; Prati, E.; Produit, N.; Rancoita, P. G.; Rapin, D.;
Raupach, F.; Recupero, S.; Ren, D.; Ren, Z.; Ribordy, M.; Richeux,
J. P.; Riihonen, E.; Ritakari, J.; Roeser, U.; Roissin, C.; Sagdeev,
R.; Santos, D.; Sartorelli, G.; Schultz von Dratzig, A.; Schwering, G.;
Seo, E. S.; Shoutko, V.; Shoumilov, E.; Siedling, R.; Son, D.; Song,
T.; Steuer, M.; Sun, G. S.; Suter, H.; Tang, X. W.; Ting, S. C. C.;
Ting, S. M.; Tornikoski, M.; Torromeo, G.; Torsti, J.; Trümper,
J.; Ulbricht, J.; Urpo, S.; Usoskin, I.; Valtonen, E.; Vandenhirtz,
J.; Velcea, F.; Velikhov, E.; Verlaat, B.; Vetlitsky, I.; Vezzu, F.;
Vialle, J. P.; Viertel, G.; Vité, D.; Von Gunten, H.; Waldmeier Wicki,
S.; Wallraff, W.; Wang, B. C.; Wang, J. Z.; Wang, Y. H.; Wiik, K.;
Williams, C.; Wu, S. X.; Xia, P. C.; Yan, J. L.; Yan, L. G.; Yang,
C. G.; Yang, M.; Ye, S. W.; Yeh, P.; Xu, Z. Z.; Zhang, H. Y.; Zhang,
Z. P.; Zhao, D. X.; Zhu, G. Y.; Zhu, W. Z.; Zhuang, H. L.; Zichichi, A.
Bibcode: 2000PhLB..472..215A
Altcode: 2000hep.ex....2049A; 2000hep.ex....2049C
The proton spectrum in the kinetic energy range 0.1 to 200 GeV
was measured by the Alpha Magnetic Spectrometer (AMS) during
space shuttle flight STS-91 at an altitude of 380km. Above the
geomagnetic cutoff the observed spectrum is parameterized by a power
law. Below the geomagnetic cutoff a substantial second spectrum
was observed concentrated at equatorial latitudes with a flux
/~70m-2s-1sr-1. Most of these second
spectrum protons follow a complicated trajectory and originate from
a restricted geographic region.
Title: Connections between neutron monitor count rate and solar
modulation strength
Authors: Usoskin, I. G.; Gladysheva, O. G.; Bobik, P.; Kudela, K.;
Kananen, H.
Bibcode: 1999CzJPh..49.1743U
Altcode:
We suggest a new approach to the normalisation of neutron monitor
response to galactic cosmic rays. The reference normalisation count
rate is the neutron monitor response to the model unmodulated flux of
galactic cosmic rays. A comparison of the actually recorded neutron
monitor count rate with the calculated normalisation count rate can
provide one with an observationally obtained true-of-date integral
measure of the current level of solar modulation of galactic cosmic
rays.
Title: Search for antihelium in cosmic rays.
Authors: Alcaraz, J.; Alvisi, D.; Alpat, B.; Ambrosi, G.; Anderhub, H.;
Ao, L.; Arefiev, A.; Azzarello, P.; Babucci, E.; Baldini, L.; Basile,
M.; Barancourt, D.; Barao, F.; Barbier, G.; Barreira, G.; Battiston,
R.; Becker, R.; Becker, U.; Bellagamba, L.; Bene, P.; Berdugo, J.;
Berges, P.; Bertucci, B.; Biland, A.; Bizzaglia, S.; Blasko, S.;
Boella, G.; Bourquin, M.; Bruni, G.; Buenerd, M.; Burger, J. D.;
Burger, W. J.; Cai, X. D.; Cavalletti, R.; Camps, C.; Cannarsa, P.;
Capell, M.; Casadei, D.; Casaus, J.; Catellini, G.; Chang, Y. H.; Chen,
H. S.; Chen, Z. G.; Chernoplekov, N. A.; Chiarini, A.; Chiueh, T. H.;
Chuang, Y. L.; Cindolo, F.; Commichau, V.; Contin, A.; Cotta-Ramusino,
A.; Crespo, P.; Cristinziani, M.; da Cunha, J. P.; Dai, T. S.; Deus,
J. D.; Ding, L. K.; Dinu, N.; Djambazov, L.; D'Antone, I.; Dong, Z. R.;
Emonet, P.; Eppling, F. J.; Eronen, T.; Esposito, G.; Extermann, P.;
Favier, J.; Feng, C. C.; Fiandrini, E.; Finelli, F.; Fisher, P. H.;
Flaminio, R.; Fluegge, G.; Fouque, N.; Galaktionov, Yu.; Gervasi, M.;
Giusti, P.; Gu, W. Q.; Guzik, T. G.; Hangarter, K.; Hasan, A.; Hermel,
V.; Hofer, H.; Huang, M. A.; Hungerford, W.; Ionica, M.; Ionica,
R.; Isbert, J.; Jongmanns, M.; Karpinski, W.; Kenney, G.; Kenny, J.;
Kim, W.; Klimentov, A.; Krieger, J.; Kossakowski, R.; Koutsenko, V.;
Laborie, G.; Laitinen, T.; Lamanna, G.; Laurenti, G.; Lebedev, A.;
Lee, S. C.; Levi, G.; Levtchenko, P.; Li, T. P.; Liu, H. T.; Lolli,
M.; Lopes, I.; Lu, G.; Lu, Y. S.; Lubelsmeyer, K.; Luckey, D.;
Lustermann, W.; Maehlum, G.; Mana, C.; Margotti, A.; Massera, F.;
Mayet, F.; McNeil, R. R.; Meillon, B.; Menichelli, M.; Mezzanotte,
F.; Mezzenga, R.; Mihul, A.; Molinari, G.; Mourao, A.; Mujunen,
A.; Palmonari, F.; Pancaldi, G.; Papi, A.; Park, I. H.; Pauluzzi,
M.; Pauss, F.; Perrin, E.; Pesci, A.; Pevsner, A.; Pilastrini, R.;
Pimenta, M.; Plyaskin, V.; Pojidaev, V.; Postema, H.; Prati, E.;
Produit, N.; Rancoita, P. G.; Rapin, D.; Raupach, F.; Recupero, S.;
Ren, D.; Ren, Z.; Ribordy, M.; Richeux, J. P.; Riihonen, E.; Ritakari,
J.; Roeser, U.; Roissin, C.; Sagdeev, R.; Santos, D.; Sartorelli, G.;
Schultz von Dratzig, A.; Schwering, G.; Shoutko, V.; Shoumilov, E.;
Siedling, R.; Son, D.; Song, T.; Steuer, M.; Sun, G. S.; Suter, H.;
Tang, X. W.; Ting, S. C. C.; Ting, S. M.; Tenbusch, F.; Torromeo,
G.; Torsti, J.; Trumper, J.; Ulbricht, J.; Urpo, S.; Usoskin, I.;
Valtonen, E.; Vandenhirtz, J.; Velikhov, E.; Verlaat, B.; Vetlitsky,
I.; Vezzu, F.; Vialle, J. P.; Viertel, G.; Vite, D.; von Gunten, H.;
Waldmeier Wicki, S.; Wallraff, W.; Wang, B. C.; Wang, J. Z.; Wang,
Y. H.; Wefel, J. P.; Werner, E. A.; Williams, C.; Wu, S. X.; Xia,
P. C.; Yan, J. L.; Yan, L. G.; Yang, C. G.; Yang, M.; Yeh, P.; Zhang,
H. Y.; Zhao, D. X.; Zhu, G. Y.; Zhu, W. Z.; Zhuang, H. L.; Zichichi, A.
Bibcode: 1999PhLB..461..387A
Altcode: 2000hep.ex....2048C; 2000hep.ex....2048A
The alpha magnetic spectrometer (AMS) was flown on the space shuttle
Discovery during flight STS-91 in a 51.7° orbit at altitudes between
320 and 390 km. A total of 2.86×106 helium nuclei were
observed in the rigidity range 1 to 140 GV. No antihelium nuclei were
detected at any rigidity. An upper limit on the flux ratio of antihelium
to helium of <1.1×10-6 is obtained.
Title: Monte-Carlo approach to Galactic Cosmic Ray propagation in
the Heliosphere
Authors: Gervasi, M.; Rancoita, P. G.; Usoskin, I. G.; Kovaltsov, G. A.
Bibcode: 1999NuPhS..78...26G
Altcode:
In the present paper we consider a possibility of using stochastic
simulation (Monte-Carlo) technique approach to the study of Galactic
Cosmic Ray propagation in the Heliosphere. We developed a technique for
calculation of the cosmic ray propagation in a spherically symmetric
steady state approximation of the Heliosphere. A comparison of the
calculation results with those obtained by other methods as well as
with an analytical approximation shows a good agreement. Besides,
in the frameworks of the approximation used, we calculated the solar
modulation of monoenergetic fluxes of Galactic Cosmic Rays entering the
Heliosphere, in the particle's energy range 0.1 - 15 GeV. We studied the
details of the modulation in their dependence of the initial particle's
energy. In particular, a linear scaling of particle's energy losses
vs. diffusion time is shown.
Title: Secondary production antiproton flux: A comparison between
interstellar models and expected flux at the Earth - presented by
M. A. C. Potenza
Authors: Boella, G.; Gervasi, M.; Potenza, M. A. C.; Rancoita, P. G.;
Usoskin, I.
Bibcode: 1999foap.conf..379B
Altcode:
No abstract at ADS
Title: Time Evolution of Solar Activity and Cosmic Ray Intensity
during the Maunder Minimum
Authors: Usoskin, I. G.
Bibcode: 1999ICRC....7..127U
Altcode: 1999ICRC...26g.127U
No abstract at ADS
Title: Modulated antiproton fluxes for interstellar production models
Authors: Boella, G.; Gervasi, M.; Potenza, M. A. C.; Rancoita, P. G.;
Usoskin, I.
Bibcode: 1998APh.....9..261B
Altcode:
Expected differential fluxes of antiprotons at the Earth's orbit are
calculated for minimum and medium strength of the solar modulation. We
used an analytical solution in the force-field approximation. Local
interstellar spectra are taken as predictions of different theoretical
models of secondary production of antiprotons in the Galaxy. All the
antiproton- as well as proton-fluxes are modulated in the same way
for the purpose of a direct comparison in order to avoid additional
uncertainties. It is shown that, in order to compare experimental data
with the existing models predictions, next generation experiments should
be able to measure fluxes of particles with energies above 100 MeV.
Title: Correlative study of solar activity and cosmic ray intensity
Authors: Usoskin, I. G.; Kananen, H.; Mursula, K.; Tanskanen, P.;
Kovaltsov, G. A.
Bibcode: 1998JGR...103.9567U
Altcode:
We perform a correlative study of solar activity (sunspot numbers)
and cosmic ray intensity (neutron monitor count rates) for the last
four solar cycles. Analysis of the running cross correlation between
the two series shows that the behavior of cosmic ray modulation is
similar, in general, for particles with different energy. However,
a strong rigidity dependence as well as an unusual behavior of the
cross correlation function is found for the descending phase of cycle
20. We study the evolution of cosmic ray and solar activity cycles
in a three-dimensional phase space by means of the delayed component
method. While all solar activity cycles and most cosmic ray cycles
are planar, cosmic ray cycle 20 is significantly three-dimensional. A
concept of the momentary phase of a cycle is introduced, and the phase
evolution of cosmic ray and solar activity cycles is studied. We also
discuss the heliospheric conditions responsible for the unusual behavior
of cosmic ray modulation in the descending phase of cycle 20.
Title: Effect of the Solar Modulation at Minimum Activity on Expected
Ratio of Antiproton to Proton Flux
Authors: Boella, G.; Gervasi, M.; Potenza, M. A. C.; Rancoita, P. G.;
Usoskin, I.
Bibcode: 1998cosm.work..273B
Altcode:
We evaluated differential fluxes of antiprotons at the Earth's
orbit. Modulated antiproton spectra are calculated for minimum
modulation strength. Local interstellar spectra are taken as predictions
of different theoretical models of secondary production of antiprotons
in the Galaxy. All the antiproton- as well as proton-fluxes are
modulated in the same way for the purpose of a direct comparison in
order to avoid additional uncertainties.
Title: Period of Unusual Modulation of Cosmic Ray Intensity: The
Declining Phase of Cycle 20
Authors: Usoskin, I. G.; Kananen, H.; Mursula, K.; Tanskanen, P.;
Kovaltsov, G. A.
Bibcode: 1997ESASP.415..491U
Altcode: 1997cpsh.conf..491U
No abstract at ADS
Title: On the Claimed 5.5-year Periodicity in Solar Activity
Authors: Mursula, K.; Usoskin, I.; Zieger, B.
Bibcode: 1997SoPh..176..201M
Altcode:
Recently, Djurovic and Pâquet (1996) claimed to have found an
oscillation with a period of about 5.5 years in several solar and
solar-terrestrial parameters, in particular in solar activity as
indicated by sunspot numbers. Since the temporal evolution of the solar
activity and solar-terrestrial environment is of great interest in many
fields, we have examined their claim in detail. We show here that their
conclusion is based on an artefact due a questionable method applied,
and due to the asymmetric form of the solar cycle. Accordingly, there
is no reasonable evidence for the existence of a fundamental 5.5-year
periodicity in solar activity.
Title: Impact of Magnetic Environment on the Generation of High-Energy
Neutrons at the Sun
Authors: Kocharov, L. G.; Torsti, J.; Tang, F.; Zirin, H.; Kovaltsov,
G. A.; Usoskin, I. G.
Bibcode: 1997SoPh..172..271K
Altcode: 1997ESPM....8..271K
This paper demonstrates the important interplanetary manifestation
of strongly tilted magnetic fields at the flare site. We start with
analysis of Big Bear Solar Observatory (BBSO) observations of magnetic
structures at sites of two flares responsible for >100 MeV neutron
events. Based on these observations, a model of neutron production is
considered. This model takes into account the observed large tilt of
magnetic field lines at footpoints of flare magnetic loops. Results
of the new calculations are compared with both previous calculations
and observations. The tilt of magnetic field lines at the flare site
is proved to be the most important parameter limiting anisotropy of
high-energy secondary emission in solar flares.
Title: The World Neutron Monitor Network as a tool for the study of
solar neutrons
Authors: Usoskin, I. G.; Kovaltsov, G. A.; Kananen, H.; Tanskanen, P.
Bibcode: 1997AnGeo..15..375U
Altcode: 1997AnG....15..375U
The use of the World Neutron Monitor Network to detect high-energy
solar neutrons is discussed in detail. It is shown that the existing
network can be used for the routine detection of intense sporadic
solar-neutron events whenever they occur. A technique is suggested
involving the weighted summation of responses of separate monitors to
solar neutrons. It is demonstrated that the use of this method improves
the significance of solar-neutron event detection. Different results of
the simulation of the neutron-monitor sensitivity to solar neutrons
have been tested with respect to their application for practical
use. It is shown that the total number of neutrons with energy above
300 MeV injected from the Sun during a solar flare can be estimated
directly from the time-integrated neutron-monitor response to solar
neutrons without any model assumptions. The estimation technique has
been developed
Title: Phase Evolution of Solar Activity and Cosmic-Ray Variation
Cycles
Authors: Usoskin, I. G.; Kovaltsov, G. A.; Kananen, H.; Mursula, K.;
Tanskanen, P. J.
Bibcode: 1997SoPh..170..447U
Altcode:
Cycles of phase evolution of solar activity and cosmic-ray variations
are reconstructed by means of the delay component method, which allows
us to study the temporal behaviour of time lag between solar activity
and cosmic-ray cycle phases. It is shown that the period of the late
20th cycle was very unusual. We have found a delay in the phase of the
solar activity cycle with respect to that of cosmic rays and discuss
the heliospheric conditions responsible for this delay.
Title: Impact of Magnetic Environment on the Generation of High-Energy
Neutrons and Gamma-Rays During Solar Flares
Authors: Kocharov, L. G.; Kovaltsov, G.; Torsti, J.; Usoskin, I.
Bibcode: 1997ICRC....1...65K
Altcode: 1997ICRC...25a..65K
No abstract at ADS
Title: Phases of Charged Particles Acceleration during Powerful
Solar Gamma-Flares Detected by the Gamma - 1
Authors: Galper, A. M.; Luchkov, B. I.; Ozerov, Yu. V.; Khodarovich,
A. M.; Rinchinov, S. B.; Kovaltsov, G. A.; Usoskin, I. G.
Bibcode: 1997ICRC....1..169G
Altcode: 1997ICRC...25a.169G
No abstract at ADS
Title: Period of Unusual Cosmic Ray Modulation in Late 20th Cycle:
Correlative Study of Cosmic Ray variations vs. Solar Activity
Authors: Usoskin, I. G.; Kovaltsov, G. A.; Kananen, H.; Mursula, K.;
Tanskanen, P.
Bibcode: 1997ICRC....2..201U
Altcode: 1997ICRC...25b.201U
No abstract at ADS
Title: Direct Deduction of the Number of Neutrons Injected from the
Sun on the Basis of Neutron Monitor Response
Authors: Kananen, H.; Kovaltsov, G. A.; Tanskanen, P.; Usoskin, I. G.
Bibcode: 1997ICRC....1...49K
Altcode: 1997ICRC...25a..49K
No abstract at ADS
Title: A Joint Analysis of High-Energy Neutrons and Neutron-Decay
Protons from a Flare
Authors: Kocharov, L. G.; Torsti, J.; Vainio, R.; Kovaltsov, G. A.;
Usoskin, I. G.
Bibcode: 1996SoPh..169..181K
Altcode:
A joint analysis of neutron monitor and GOES data is performed to
study the production of high-energy neutrons at the Sun. The main
objects of the research are the spectrum of >50 MeV neutrons and
a possible spectrum of primary (interacting) protons which produced
those neutrons during the major 1990 May 24 solar flare. Different
possible scenarios of the neutron production are presented. The high
magnitude of the 1990 May 24 neutron event provided an opportunity to
detect neutron decay protons of higher energies than ever before. We
compare predictions of the proposed models of neutron production with
the observations of protons on board GOES 6 and 7. It is shown that the
`precursor' in high-energy GOES channels observed during 20:55-21:09 UT
can be naturally explained as originating from decay of neutrons in the
interplanetary medium. The ratio of counting rates observed in different
GOES channels can ensure the selection of the model parameters.
Title: The 1990 May 24 solar flare and cosmic ray event
Authors: Kocharov, Leon; Kovaltsov, Gennadi; Torsti, Jarmo; Usoskin,
Ilya; Zirin, Harold; Anttila, Antti; Vainio, Rami
Bibcode: 1996AIPC..374..246K
Altcode: 1996hesp.conf..246K
We have analyzed data on solar protons, neutrons, electrons, gamma-ray,
optical and microwave emissions for the 1990 May 24 solar flare. Taking
into account high energy neutron and gamma-ray observations, we have
suggested two neutron injections occurred during the flare. These two
injections are called f- (first) and s- (second). Two components of
interacting protons correspondingly existed to produce these neutrons
at the Sun. The flare gave also a rise to solar cosmic ray event, which
was detected by the neutron monitor network and GOES satellites. Two
components of protons were observed in the interplanetary medium (p-
(prompt) and d- (delayed) components). A possible spectrum of the
s-component of interacting protons coincided with injection spectrum
of p-component of interplanetary protons. For this reason, s- and p-
components of protons may be considered as different portions of a
single population of accelerated particles in the solar corona. The
net result is that three proton components (f-, p/s-, and d-) were
accelerated during flare process developing from the Sun to the
interplanetary medium.
Title: Temporal and spectral characteristics of solar gamma flares
observed in the Gamma-1 experiment.
Authors: Galper, A. M.; Zverev, V. G.; Luchkov, B. I.; Ozerov, Yu. V.;
Khodarovitch, A. M.; Kovaltsov, G. A.; Usoskin, I. G.
Bibcode: 1996JMoPS...6..399G
Altcode:
The results of a comparative analysis of the high-energy (Eγ >
30 MeV) powerful solar gamma flares of 26.03.91 and 15.06.91 are
presented. These flares are estimated to have an active phase with
an exponential intensity decay lasting up to 10 minutes (and possibly
more for 15.06.91) and repeated multiple acts of electron and proton
acceleration, followed by a longer phase without such repeated multiple
acts of acceleration. Limits on parameters for particle acceleration and
propagation in the solar atmosphere are estimated from the observational
data for these flares.
Title: Erratum: The 1991 March 22 Flare: Possible Anistrophy of
High-Energy Neutral Emission
Authors: Kocharov, L. G.; Lee, Jeongwoo W.; Wang, H.; Zirin, H.;
Kovaltsov, G. A.; Usoskin, I. G.
Bibcode: 1995SoPh..161..407K
Altcode:
No abstract at ADS
Title: Neutron Monitor Data on the 15 June 1991 Flare: Neutrons as
a Test for Proton Acceleration Scenario
Authors: Kovaltsov, G. A.; Usoskin, I. G.; Kocharov, L. G.; Kananen,
H.; Tanskanen, P. J.
Bibcode: 1995SoPh..158..395K
Altcode:
Response of Alma-Ata neutron monitor for solar neutrons from the
15 June 1991 was studied. We considered this response as a test for
various scenarios of proton acceleration during the flare. The analysis
of neutron monitor is an evidence in favour of the assumption of two
acts of proton acceleration at impulsive and post-impulsive phases of
the flare.
Title: The 1991 March 22 Flare: Possible Anisotropy of High-Energy
Neutral Emission
Authors: Kocharov, L. G.; Lee, Jeongwoo W.; Wang, H.; Zirin, H.;
Kovaltsov, G. A.; Usoskin, I. G.
Bibcode: 1995SoPh..158...95K
Altcode:
We made a parameter fit to the Haleakala neutron monitor counting
rate during the 1991 March 22 solar flare (Pyle and Simpson, 1991)
using the time profiles of γ-rays at 0.42-80 MeV obtained with
the GRANAT satellite (Vilmeret al., 1994) and the microwave data
from Owens Valley Radio Observatory. We use a two-component neutron
injection function to find that either an impulsive injection or the
`impulsive-plus-prolonged' neutron injection is possible. In both
cases, the number of > 300 MeV neutrons emitted towards the Earth
is estimated as ≈ 2 × 1027 sr−1, which is
less than that of the 1990 May 24 flare by an order of magnitude.
Title: Correlative Investigations of the 1990 May 24 Solar Flare
Authors: Kocharov, L. G.; Kovaltsov, G. A.; Torsti, J.; Usoskin,
I. G.; Zirin, H.
Bibcode: 1995ICRC....4..159K
Altcode: 1995ICRC...24d.159K
No abstract at ADS
Title: High Energy Neutrons from the June 15, 1991 Solar Flare as
Detected by the Neutron Monitor
Authors: Usoskin, I. G.; Kovaltsov, G. A.; Kocharov, L. G.; Kananen,
H.; Tanskanen, P.
Bibcode: 1995ICRC....4..151U
Altcode: 1995ICRC...24d.151U
No abstract at ADS
Title: The June 3, 1982 Solar Flare as a Test for Neutron Monitor
Sensitivity for Solar Neutrons
Authors: Kananen, H.; Kocharov, L. G.; Kovaltsov, G. A.; Tanskanen,
P.; Usoskin, I. G.
Bibcode: 1995ICRC....4..147K
Altcode: 1995ICRC...24d.147K
No abstract at ADS
Title: Two Injections of High Energy Neutrons during the May 24,
1990 Solar Flare
Authors: Kovaltsov, G. A.; Kocharov, L. G.; Usoskin, I. G.; Kananen,
H.; Taskanen, P.
Bibcode: 1995ICRC....4..155K
Altcode: 1995ICRC...24d.155K
No abstract at ADS
Title: High-energy gamma-ray signature of proton acceleration during
1991 June 15 solar flare
Authors: Kocharov, G. E.; Chuikin, E. I.; Kovaltsov, G. A.; Usoskin,
I. G.; Kocharov, L. G.
Bibcode: 1994AIPC..294...45K
Altcode: 1994hesp.conf...45K
We consider the γ-ray and radio observations for the 06.15.1991
flare. It is shown that these data give the first possibility for
precise determination of proton spectrum in 10 MeV-10 GeV energy range
in flare site. The power law γ-ray spectrum up to 1 GeV indicates
that the maximum energy in power law primary proton spectrum is >=10
GeV. The time profiles of cm-radioemission and of γ-ray in 0.8-10 MeV
energy band and above 50 MeV coincide. A continuous and simultaneous
acceleration of protons and relativistic electrons at the gradual
phase of the flare gives a natural explanation of the data.
Title: Neutron and electromagnetic emissions during the 1990 May 24
solar flare
Authors: Kocharov, L. G.; Lee, Jeongwoo W.; Zirin, H.; Kovaltsov,
G. A.; Usoskin, I. G.; Pyle, K. R.; Shea, M. A.; Smart, D. F.
Bibcode: 1994SoPh..155..149K
Altcode:
In this paper, we are primarily concerned with the solar neutron
emission during the 1990 May 24 flare, utilizing the counting rate
of the Climax neutron monitor and the time profiles of hard X-rays
and γ-rays obtained with the GRANAT satellite (Pelaezet al., 1992;
Talonet al., 1993; Terekhovet al., 1993). We compare the derived
neutron injection function with macroscopic parameters of the flare
region as obtained from theHα and microwave observations made at the
Big Bear Solar Observatory and the Owens Valley Radio Observatory,
respectively. Our results are summarized as follows: (1) to explain the
neutron monitor counting rate and 57.5-110 MeV and 2.2 MeV γ-ray time
profiles, we consider a two-component neutron injection function,Q(E,
t), with the form Q(E,t) = Nfexp[-E/Ef
-t/Tf] + N2 exp[-E/Es -
t/Ts], where Nf(s),Ef(s),
andTf(s) denote number, energy, and decay time of the fast
(slow) injection component, respectively. By comparing the calculated
neutron counting rate with the observations from the Climax neutron
monitor we derive the best-fit parameters asTf ≈ 20
s,Ef ≈ 310 MeV,Ts ≈ 260 s,Es
≈ 80 MeV, andNf(E > 100 MeV)/Ns(E >
100 MeV) ≈ 0.2. (2) From the Hα observations, we find a relatively
small loop of length ≈ 2 × 104 km, which may be regarded
as the source for the fast-decaying component of γ-rays (57.5-110
MeV) and for the fast component of neutron emission. From microwave
visibility and the microwave total power spectrum we postulate the
presence of a rather big loop (≈ 2 × 105 km), which we
regard as being responsible for the slow-decaying component of the
high-energy emission. We show how the neutron and γ-ray emission
data can be explained in terms of the macroscopic parameters derived
from the Hα and microwave observations. (3) The Hα observations
also reveal the presence of a fast mode MHD shock (the Moreton wave)
which precedes the microwave peak by 20-30 s and the peak of γ-ray
intensity by 40-50 s. From this relative timing and the single-pulsed
time profiles of both radiations, we can attribute the whole event
as due to a prompt acceleration of both electrons and protons by the
shock and subsequent deceleration of the trapped particles while they
propagate inside the magnetic loops.
Title: Generation of neutrons during the solar flare of May 24, 1990
Authors: Koval'Tsov, G. A.; Kocharov, G. E.; Kocharov, L. G.; Usoskin,
I. G.
Bibcode: 1994AstL...20..658K
Altcode: 1994PAZh...20..762K
No abstract at ADS
Title: Electromagnetic and corpuscular emission from the solar flare
of 1991 June 15: Continuous acceleraton of relativistic particles
Authors: Kocharov, L. G.; Kovaltsov, G. A.; Kocharov, G. E.; Chuikin,
E. I.; Usoskin, I. G.; Shea, M. A.; Smart, D. F.; Melnikov, V. F.;
Podstrigach, T. S.; Armstrong, T. P.; Zirin, H.
Bibcode: 1994SoPh..150..267K
Altcode:
Data on X-,γ-ray, optical and radio emission from the 1991 June
15 solar flare are considered. We have calculated the spectrum of
protons that producesγ-rays during the gradual phase of the flare. The
primary proton spectrum can be described as a Bessel-function-type up
to 0.8 GeV and a power law with the spectral index ≈3 from 0.8 up
to 10 GeV or above. We have also analyzed data on energetic particles
near the Earth. Their spectrum differed from that of primary protons
producingγ-ray line emission. In the gradual phase of the flare
additional pulses of energy release occurred and the time profiles of
cm-radio emission andγ-rays in the 0.8-10 MeV energy band and above 50
MeV coincided. A continuous and simultaneous stochastic acceleration
of the protons and relativistic electrons at the gradual phase of the
flare is considered as a natural explanation of the data.
Title: Gamma-radiation from the solar flare of 15 June 1991 as
evidence of long-term acceleration of protons up to 10 GeV
Authors: Koval'Tsov, G. A.; Kocharov, G. E.; Kocharov, L. G.;
Mel'Nikov, V. F.; Podstrigach, T. S.; Usoskin, I. G.; Chujkin, E. I.
Bibcode: 1993RoIzF..57..138K
Altcode:
The power spectrum of gamma-radiation up to 2 GeV observed during the
flare of 15 June 1991 indicates that the primary protons had a power
spectrum extending at least to 10 GeV. Comparing the time profiles
of centimeter-wave emission, gamma-radiation in nuclear lines in the
0.8-8 MeV range, and high-energy gamma-radiation from pion decay,
their coincidence is found, indicating the simultaneous long-term
acceleration of particles after the impulsive phase of the solar flare.
Title: Detection of solar neutrinos by the worldwide network of
neutron monitors
Authors: Efimov, Yu. E.; Koval'Tsov, G. A.; Kocharov, G. E.; Kocharov,
L. G.; Usoskin, I. G.
Bibcode: 1993RoIzF..57..142E
Altcode:
The possibility of detecting solar neutrinos by the worldwide network
of neutron monitors is examined. The neutron-monitor response function
to high-energy solar neutrinos is reexamined. It is shown that the
probability of detecting high-energy solar neutrinos with the worldwide
neutron-monitor network is higher than previously thought.
Title: High Energy Gamma Rays from 1991 June 15 Solar Flare as
Evidence of Proton Acceleration up to 10 GeV
Authors: Kocharov, G. E.; Chuikin, E. I.; Kocharov, L. G.; Kovaltsov,
G. A.; Melnikov, V. F.; Podstrigach, T. S.; Usoskin, I. G.
Bibcode: 1993ICRC....3..123K
Altcode: 1993ICRC...23c.123K
No abstract at ADS
Title: Solar Flare Neutrinos
Authors: Kocharov, G. E.; Kovaltsov, G. A.; Usoskin, I. G.
Bibcode: 1991ICRC....3..752K
Altcode: 1991ICRC...22c.752K
No abstract at ADS
Title: Solar flare neutrinos.
Authors: Kocharov, G. E.; Koval'Tsov, G. A.; Usoskin, I. G.
Bibcode: 1991NCimC..14..417K
Altcode:
The theory of high-energy neutrinos generation in the solar atmosphere
during flares is developed. A possible effect in different neutrino
detectors is discussed.
Title: On the Dimension of Solar Attractor
Authors: Ostriakov, V. M.; Usoskin, I. G.
Bibcode: 1990SoPh..127..405O
Altcode:
Analyzing the average over a year (a) and over a month (b) of Wolf
numbers and radiocarbon data (c), we have obtained the dimensions d
of the solar attractor which are: 3.3 (a), 4.3 (b), 4.7 (c). During
the Maunder minimum such a dimension turns out to be significantly
higher: 8.0 (c); whereas during the period of a phase catastrophe
(1792-1828) Wolf numbers averaged over a month yield d = 3.0 (b). We
have also investigated the sensitivity of our inferences to the number
of available experimental points. Positive values of the Kolmogorov
entropy and first Lyapunov exponent explicitly show the stochastic
behaviour of the Sun.
Title: On the dimension of the solar attractor.
Authors: Ostryakov, V. M.; Usoskin, I. G.
Bibcode: 1988BSolD1988...91O
Altcode:
Analysing the year-averaged (a), monthly-averaged (b) Wolf numbers
and radio carbon data (c) the authors have obtained dimensions d of
the solar attractor which are: 3.25 (a), 4.3 (b), 4.7 (c). During the
Maunder minimum the dimension turns out to be sufficiently higher:
7.5 (c) whereas during the period of phase catastrophe (1792 - 1828)
monthly-averaged Wolf numbers give d = 3.0 (b). Some consequences
of calculations for modulation of galactic CR by solar activity are
discussed.