Author name code: krijger ADS astronomy entries on 2022-09-14 author:"Krijger, J." ------------------------------------------------------------------------ Title: The New SCIAMACHY Reference Solar Spectral Irradiance and Its Validation Authors: Hilbig, T.; Weber, M.; Bramstedt, K.; Noël, S.; Burrows, J. P.; Krijger, J. M.; Snel, R.; Meftah, M.; Damé, L.; Bekki, S.; Bolsée, D.; Pereira, N.; Sluse, D. Bibcode: 2018SoPh..293..121H Altcode: This paper describes a new reference solar spectrum retrieved from measurements of the satellite instrument SCIAMACHY in the wavelength region from 0.24 μ m to 2.4 μ m and its comparison with several other established solar reference spectra. The SCIAMACHY reference spectrum was recorded early in the mission before substantial optical degradation due to the harsh space environment sets in. The radiometric calibration of SCIAMACHY, applied in this study, includes a physical model of the scanner unit. Furthermore, SCIAMACHY's internal white light source (WLS) is used to correct for on-ground to in-flight changes. The resultant calibrated solar spectrum from SCIAMACHY is in good agreement with several available solar spectral irradiance (SSI) references in the visible spectral range. Strong throughput losses due to detector icing in the near infrared (NIR) are now adequately accounted for. Nevertheless, a deficit with respect to the ATLAS-3 composite and SORCE/SIM SSI is observed in the NIR. However, the SCIAMACHY solar reference spectrum agrees well with the recently re-evaluated SOLAR/SOLSPEC-ISS and recent ground measurements taken at Mauna Loa in the NIR. Title: Improved Correction for Contamination-Induced In-Flight Instrument Degradation of SCIAMACHY Authors: Snel, R. C.; Krijger, J. M. Bibcode: 2015ESASP.735E..13S Altcode: SCIAMACHY suffers from degradation due to contamination of the scan mirror surfaces, optical components in the Optical Bench Module, and detector surfaces.We have improved the polarisation and degradation description of the instrument as well as the optical ground support equipment used for initial on-ground instrument calibration. This allows for a consistent model of the instrument for both on-ground and in-flight conditions, and for arbitrary amounts of contamination of the instrument.Using this model we have re-analysed the in-flight calibration and monitoring data to arrive at an improved description of the throughput and polarisation sensitivity of SCIAMACHY, for any time during its mission. Title: The new SCIAMACHY calibration and degradation approach and validation Authors: Krijger, J. M. Matthijs; Snel, R.; Bovensmann, H.; Eichmann, K. U.; Noel, S.; Liebing, P.; Richter, A.; Buchwitz, M.; von Savigny, C.; Rozanov, A.; Bramstedt, K.; Gerilowski, K.; Vountas, M.; Burrows, J. P.; van der Meer, P.; van Hees, R.; Aben, I.; Lichtenberg, G.; Slijkhuis, S.; Doicu, A.; Schreier, F.; Hrechanyy, S.; Kretschel, K.; Meringer, M.; Hess, M.; Gottwald, M.; Aberle, B.; Scherbakov, D.; Gimeno-Garcia, S.; van Gijsel, J. A. E.; Tilstra, L. G.; Lerot, C.; Van Roozendael, M.; Dehn Serco, A.; Fehr, T. Bibcode: 2010cosp...38..101K Altcode: 2010cosp...38..101M; 2010cosp.meet..101K This presentation covers the highlights of the radiance, irradiance, polarisation and degrada-tion re-characterisation of SCIAMACHY and its validation. The imaging spectrometer SCIA-MACHY on ENVISAT has been collecting data since launch in 2002. Over the years the exposure to space has affected the optical performance and rendered the on-ground calibra-tion data increasingly more outdated. As the overall calibration quality is continuously being improved through better in-flight characterisation and updated algorithms, instrument aspects with previously acceptable errors are now in need of improvement. This required re-analysis of the on-ground calibration measurements, and pivots on measurements which were initially not intended for this type of calibration and an improved mirror-model for the scanner unit. Ad-ditionally, with the new approach it is possible to derive scan-angle dependended degradation-corrected calibration key data for the contaminated mirror surfaces in the scanner unit, thus improving the radiometric, polarisation, and scan-angle calibration of the instrument. We will present the new calibration approach and the first results of the validation. Title: Observations of Umbral Flashes Authors: Rouppe van der Voort, L. H. M.; Krijger, J. M. Bibcode: 2003csss...12..607R Altcode: We present observations of oscillations in the chromosphere of the umbra of sunspots. The observations were obtained with the Swedish Vacuum Solar Telescope (SVST) and the Dutch Open Telescope (DOT) on La Palma, comprising spectrograms and filtergrams in the Ca II H line. The sawtooth pattern in the spectroscopic time evolution of the Ca II H core is shown as well as evidence for a connection between umbral flashes and running penumbral waves from image sequences. Running waves, coherent over a large fraction of the penumbra, seem to be excited by flashes that occur close to the umbra-penumbral boundary. Comparing the intensity oscillations in the Ca II H line with TRACE observations in the 1600 Å passband, we find a phase difference of approximately 25 ° with 1600 Å leading the Ca II H intensity oscillation which we attribute to complex dynamical behaviour. Title: Dynamics of the solar chromosphere IV. Evidence for atmospheric gravity waves from TRACE Authors: Rutten, R. J.; Krijger, J. M. Bibcode: 2003A&A...407..735R Altcode: We study the low-frequency brightness modulation of internetwork regions in the low solar chromosphere using simultaneous ultraviolet and white-light image sequences from the Transition Region and Coronal Explorer (TRACE). The ultraviolet sequences exhibit a slowly varying brightness pattern in internetwork regions on which the more familiar acoustic three-minute oscillation is superimposed, with about half of the peak brightness reached in internetwork grains contributed by the low-frequency background. We address the nature of the latter, applying two-dimensional Fourier filtering to isolate it from the acoustic modulation. Spatio-temporal comparisons and selective time-delay scatter correlations between the ultraviolet and white-light low-frequency sequences establish that reversed granulation constitutes at most a minor part of the ultraviolet background. Fourier analysis shows that the meso-scale contribution dominates and consists of atmospheric gravity waves. Title: La Palma observations of umbral flashes Authors: Rouppe van der Voort, L. H. M.; Rutten, R. J.; Sütterlin, P.; Sloover, P. J.; Krijger, J. M. Bibcode: 2003A&A...403..277R Altcode: We present high-quality Ca II H & K data showing chromospheric flashes in sunspot umbrae collected with the Swedish Vacuum Solar Telescope, the Dutch Open Telescope, and the Swedish 1-m Solar Telescope at the Roque de los Muchachos Observatory on La Palma. Differential movies, time slices, spectrograms, and Fourier power maps demonstrate that umbral flashes and running penumbral waves are closely related oscillatory phenomena, combining upward shock propagation with coherent wave spreading over the entire spot. We attribute the flash brightening to large redshift by post-shock material higher up. We find no obvious relation between umbral dots and umbral flashes. Title: Photospheric flows measured with TRACE II. Network formation Authors: Krijger, J. M.; Roudier, T. Bibcode: 2003A&A...403..715K Altcode: We analyse a 7 d (167 h) sequence of TRACE white-light images with 1 arcsec angular resolution taken at 1 min cadence. The TRACE resolution and the fast cadence allows us to produce maps of the horizontal flow fields with high angular (1 arcsec) and temporal resolution (5 min). The field of view of 128arcsec x 128arcsec (~93 Mm x 93 Mm) covers approximately an area of 10 to 30 supergranules. This area was followed during solar rotation. Magnetic flux was artificially inserted into the successive flow maps in the form of ephemeral regions with positive and negative polarity. The emergence rate of 2 x 1022 Mx h-1 with an average flux per region of about 1.1 x 1019 Mx produces a good reproduction of the chromospheric network as observed in images taken simultaneously at 1600 Å. In addition, we show that the quiet network can be maintained only if field elements of both polarities are inserted into the flow fields. Our analysis suggests that the network is fully replenished on a time scale of a day and the lifetimes of the magnetic elements are of a similar duration. Title: Verification of SCIAMACHY's Polarisation Correction over the Sahara Desert Authors: Tilstra, L. G.; Acarreta, J. R.; Krijger, J. M.; Stammes, P. Bibcode: 2003ESASP.531E..13T Altcode: No abstract at ADS Title: Current Status of SCIAMACHY Polarisation Measurements Authors: Krijger, J. M.; Stammes, P. Bibcode: 2003ESASP.531E..14K Altcode: No abstract at ADS Title: The "careers in solar physics" session of the SPM10 meeting Authors: Aulanier, G.; Parenti, S.; Krijger, J. M. Bibcode: 2002ESASP.506..981A Altcode: 2002ESPM...10..981A; 2002svco.conf..981A During the SPM10 meeting held in Prague (Czech Republic) on September 9-14, 2002, a half-day 'young session' was organized on the topic of careers in solar physics. Several young researchers and senior scientists were invited to give oral contributions on the current advantages and difficulties attached to the current system for post-doctoral contracts. A scientist from USA also presented the American system for contractors, and an ESA representative presented the official position of ESA regarding funding researchers. From the talks as well as from the long open discussion which followed, it was widely agreed that several typical rules for EU post-doc contracts (their short duration, their mandatory mobility, their age limit and their administrative and financial difficulties) not only lead to serious problems in the private life of postdocs, but essentially can have serious drawbacks on the follow-up of long-term scientific developments, and could quickly result in a dramatic loss of expertise, from the scale of individual institutes to the European scientific community at large. Many participants and most of the young researchers naturally agreed that new longer-term, renewable and stable contracts are necessary. In order to create such types of contracts, several fund raising initiative achieveable by the scientific community were discussed. The development of better public outreach initiatives on the European scale was a possibility which federated most of the participants. The resulting conclusion on this session were transmitted to the new board of the Solar Physics Section of the EAS/SPS. Title: Origin and evolution of ices around massive young stars Authors: Krijger, Johannes Mattheus Bibcode: 2002PhDT.......215K Altcode: The thesis Structure and dynamics of the solar chromosphere of J.M. Krijger is a study on the behavior of the solar chromosphere, the thin layer just above the solar surface (photosphere) visible in purple red light during a total solar eclipse. The most important result of this thesis is that the chromosphere is filled with acoustic and internal gravity waves that travel upward until they collide with a canopy of expanding magnetic field. The photosphere is the layer of which we see the light with the naked eye. Through this layer poke large and small magnetic tubes. Above the photosphere and the chromosphere sits the hot solar corona of a few million degrees. With observations of among others the space satellite TRACE (Transition Region and Coronal Explorer) J.M. Krijger shows that the photosphere is dominated by flows of the ambient gas that dictate the magnetic field where to go. The possible heating of the chromosphere is an important unsolved problem in solar physics. The chromosphere forms the transition region between the very hot corona, dominated by magnetic fields, and the photosphere where gasflows drag the magnetic field along. In this transition region the magnetic field, which in the photosphere is still trapped in individual tubes, expands to a canopy above which the magnetic field fills the entire space. In this thesis it is shown that the chromosphere is dominated by upward propagating acoustic waves and a magnetic canopy that changes the dynamics of the oscillations. Finally J.M. Krijger shows that the network of magnetic field in the chromosphere is formed by magnetic tubes that are swepped together by flows in the photosphere. Title: Photospheric flows measured with TRACE Authors: Krijger, J. M.; Roudier, T.; Rieutord, M. Bibcode: 2002A&A...387..672K Altcode: We analyse white-light image sequences taken with the Transition Region and Coronal Explorer (TRACE) using an optimised local correlation tracking (LCT) method to measure the horizontal flows in the quiet solar photosphere with high spatial (1 arcsec) and temporal (5 min) resolution. Simultaneously taken near-ultraviolet images from TRACE confirm that our LCT-determined flows recover the actual supergranulation pattern, thus proving that the topology of the horizontal flow distribution and network assembly may be studied from long-duration TRACE white-light sequences with our method. Title: Structure and dynamics of the solar chromosphere Authors: Krijger, Johannes Mattheus Thijs Bibcode: 2002PhDT.......228K Altcode: No abstract at ADS Title: Dynamics of the solar chromosphere. III. Ultraviolet brightness oscillations from TRACE Authors: Krijger, J. M.; Rutten, R. J.; Lites, B. W.; Straus, Th.; Shine, R. A.; Tarbell, T. D. Bibcode: 2001A&A...379.1052K Altcode: We analyze oscillations in the solar atmosphere using image sequences from the Transition Region and Coronal Explorer (TRACE) in three ultraviolet passbands which sample the upper solar photosphere and low chromosphere. We exploit the absence of atmospheric seeing in TRACE data to furnish comprehensive Fourier diagnostics (amplitude maps, phase-difference spectra, spatio-temporal decomposition) for quiet-Sun network and internetwork areas with excellent sampling statistics. Comparison displays from the ground-based Ca Ii H spectrometry that was numerically reproduced by Carlsson & Stein are added to link our results to the acoustic shock dynamics in this simulation. The TRACE image sequences confirm the dichotomy in oscillatory behaviour between network and internetwork and show upward propagation above the cutoff frequency, the onset of acoustic shock formation in the upper photosphere, phase-difference contrast between pseudo-mode ridges and the interridge background, enhanced three-minute modulation aureoles around network patches, a persistent low-intensity background pattern largely made up of internal gravity waves, ubiquitous magnetic flashers, and low-lying magnetic canopies with much low-frequency modulation. The spatio-temporal occurrence pattern of internetwork grains is found to be dominated by acoustic and gravity wave interference. We find no sign of the high-frequency sound waves that have been proposed to heat the quiet chromosphere, but such measurement is hampered by non-simultaneous imaging in different passbands. We also find no signature of particular low-frequency fluxtube waves that have been proposed to heat the network. However, internal gravity waves may play a role in their excitation. Title: Phase Relations between Chromospheric and Transition Region Oscillations Authors: Krijger, J. M.; Curdt, W.; Heinzel, P.; Schmidt, W. Bibcode: 2000ESASP.463..353K Altcode: 2000sctc.proc..353K No abstract at ADS Title: COMPTEL detection of pulsed gamma -ray emission from PSR B1509-58 up to at least 10 MeV Authors: Kuiper, L.; Hermsen, W.; Krijger, J. M.; Bennett, K.; Carramiñana, A.; Schönfelder, V.; Bailes, M.; Manchester, R. N. Bibcode: 1999A&A...351..119K Altcode: 1999astro.ph..3474K We report on the first firm detection of pulsed gamma -ray emission from PSR B1509-58 in the 0.75-30 MeV energy range in CGRO COMPTEL data collected over more than 6 years. The modulation significance in the 0.75-30 MeV pulse-phase distribution is 5.4sigma and the lightcurve is similar to the lightcurves found earlier between 0.7 and 700 keV: a single broad asymmetric pulse reaching its maximum 0.38 +/- 0.03 in phase after the radio peak, compared to the offset of 0.30 found in the CGRO BATSE soft gamma-ray data, and 0.27 +/- 0.01 for RXTE (2-16 keV), compatible with ASCA (0.7-2.2 keV). Analysis in narrower energy windows shows that the single broad pulse is significantly detected up to ~ 10 MeV. Above 10 MeV we do detect marginally significant (2.1sigma ) modulation with an indication for the broad pulse. However, imaging analysis shows the presence of a strong 5.6sigma source at the position of the pulsar. To investigate this further, we have also analysed contemporaneous CGRO EGRET data (>30 MeV) collected over a nearly 4 year period. In the 30-100 MeV energy window, adjacent to the COMPTEL 10-30 MeV range, a 4.4sigma source can be attributed to PSR B1509-58. Timing analysis in this energy window yields an insignificant signal of 1.1sigma , but with a shape somewhat similar to that of the COMPTEL 10-30 MeV lightcurve. Combining the two pulse-phase distributions results in a suggestive double-peaked pulsed signal above the background level estimated in the spatial analyses, with one broad peak near phase 0.38 (aligned with the pulse observed at lower energies) and a second narrower peak near phase 0.85, which is absent for energies below 10 MeV. The modulation significance is, however, only 2.3sigma and needs confirmation. Spectral analysis based on the excess counts in the broad pulse of the lightcurve shows that extrapolation of the OSSE power-law spectral fit with index -1.68 describes our data well up to 10 MeV. Above 10 MeV the spectrum breaks abruptly. The precise location of the break/bend between 10 and 30 MeV depends on the interpretation of the structure in the lightcurve measured by COMPTEL and EGRET above 10 MeV. Such a break in the spectrum of PSR B1509-58 has recently been interpreted in the framework of polar cap models for the explanation of gamma-ray pulsars, as a signature of the exotic photon splitting process in the strong magnetic field of PSR B1509-58. For that interpretation our new spectrum constrains the co-latitude to ~ 2degr , close to the ``classical'' radius of the polar cap. In the case of an outer-gap scenario, our spectrum requires a dominant synchrotron component. Title: Dynamics Of The Internetwork Chromosphere With TRACE Authors: Krijger, J. M. Bibcode: 1999ESASP.446..391K Altcode: 1999soho....8..391K The UV passbands of the Transition Region and Coronal Explorer (TRACE; 170 nm, 160 nm, 155 nm, respectively) sample the low chromosphere. Quiet-sun regions display brightness patterning much like Ca II H &K, including internetwork grains akin to the so-called K2v grains. We demonstrate this pattern correspondence with simultaneous TRACE and La Palma data, study and we Fourier-analyze high-cadence TRACE image sequences to obtain power, coherence and phase difference spectra, separately for network and internetwork. Title: COMPTEL Detection of Pulsed Emission from PSR B1509-58 up to at Least 10 Mev Authors: Kuiper, L.; Hermsen, W.; Krijger, J. M.; Bennett, K.; Schönfelder, V.; Carramiñana, A.; Manchester, R.; Bailes, M. Bibcode: 1999ApL&C..38...33K Altcode: 1998astro.ph.12405K We report the COMPTEL detection of pulsed $\gamma$-emission from PSR B1509-58 up to at least 10 MeV using data collected over more than 6 years. The 0.75-10 MeV lightcurve is broad and reaches its maximum near radio-phase 0.38, slightly beyond the maximum found at hard X-rays/ soft $\gamma$-rays. In the 10-30 MeV energy range a strong source is present in the skymap positionally consistent with the pulsar, but we do not detect significant pulsed emission. However, the lightcurve is consistent with the pulse shape changing from a single broad pulse into a double-peak morphology. Our results significantly constrain pulsar modelling.