E-Print Archive

There are 3784 abstracts currently viewable.


Search:

Advanced Search
Options
Main Page Add New E-Print Submitter
Information
Feedback
News Help/FAQ About Preferences
Manage Key Phrase
Notification
Minima of Solar Cycles 22/23 and 23/24 as Seen in SOHO/CELIAS/SEM Absolute Solar EUV Flux  

Leonid Didkovsky   Submitted: 2009-11-04 09:54

Verified and updated calibrated absolute solar flux in the He II 30.4 nm spectral band-pass as measured by the Solar EUV Monitor (SEM) allows us to study variations of the solar EUV irradiance near the minima of Solar Cycles 22/23 and 23/24. Based on eight (1996 to 2007) NASA sounding rocket flights, a comparison of SEM data with the measurements from three independent EUV instruments was performed to verify and confirm the accuracy of the published SEM data. SEM calibrated data were analyzed to determine and compare minima for solar cycles 22/23 and 23/24. The minima points were calculated using SEM first order daily averaged flux smoothed by a running mean (RM) filter with the window of averaging equal to 365 days. These minima occurred on June 2, 1996 (22/23) and November 28, 2008 (23/24). The 23/24 minimum showed about 15% lower EUV flux in the 30.4 nm band-pass than the 22/23 minimum. The 365-day RM curve around the 23/24 minimum has significant asymmetry (fast decrease of the EUV flux to the minimum and a long, near-horizontal profile after the minimum). This profile is quite different from the much faster and symmetrical change of the flux around the 22/23 minimum. SEM flux was compared with both high spectral resolution (0.1 nm) Mg II index calculated from the Solar Radiation and Climate Experiment (SORCE) using the Solar Stellar Irradiance Comparison Experiment (SOLSTICE) data and with the NOAA composite Mg II index spectrum.

Authors: Leonid Didkovsky, Darrell Judge, Seth Wieman, Don McMullin
Projects: None

Publication Status: ASP Conf. Series, submitted
Last Modified: 2009-11-04 10:23
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

EUV SpectroPhotometer (ESP) in Extreme Ultraviolet Variability Experiment  

Leonid Didkovsky   Submitted: 2009-11-03 20:33

The Extreme ultraviolet SpectroPhotometer (ESP) is one of five channels of the Extreme ultraviolet Variability Experiment (EVE) onboard the NASA Solar Dynamics Observatory (SDO). The ESP channel design is based on a highly stable diffraction transmission grating and is an advanced version of the Solar Extreme ultraviolet Monitor (SEM), which has been successfully observing solar irradiance onboard the Solar and Heliospheric Observatory (SOHO) since December 1995. ESP is designed to measure solar Extreme UltraViolet (EUV) irradiance in four first order bands of the diffraction grating centered around 19 nm, 25 nm, 30 nm, and 36 nm, and in a soft X-ray band from 0.1 to 7.0 nm in the zeroth order of the grating. Each band's detector system converts the photo-current into a count rate (frequency). The count rates are integrated over 0.25 sec increments and transmitted to the EVE Science and Operations Center for data processing. An algorithm for converting the measured count rates into solar irradiance and the ESP calibration parameters are described. The ESP pre-flight calibration was performed at the Synchrotron Ultraviolet Radiation Facility of the National Institute of Standards and Technology. Calibration parameters were used to calculate absolute solar irradiance from the Sounding Rocket flight measurements on 14 April 2008. These irradiances for the ESP bands closely match the irradiance determined for two other EUV channels flown simultaneously, EVE's Multiple Euv Grating Spectrograph (MEGS) and SOHO's Charge, Element and Isotope Analysis System / Solar EUV Monitor (CELIAS/SEM).

Authors: Leonid Didkovsky, Darrell Judge, Seth Wieman, Tom Woods, Andrew Jones
Projects: None

Publication Status: Solar Physics (accepted)
Last Modified: 2009-11-04 08:43
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Correction of SOHO CELIAS/SEM EUV Measurements saturated by extreme solar flare events  

Leonid Didkovsky   Submitted: 2006-10-04 12:10

The solar irradiance in the Extreme Ultraviolet (EUV) spectral bands has been observed with a 15 sec cadence by the SOHO Solar EUV Monitor (SEM) since 1995. During remarkably intense solar flares the SEM EUV measurements are saturated in the central (zero) order channel (0.1 - 50.0 nm) by the flare soft X-ray and EUV flux. The first order EUV channel (26 - 34 nm) is not saturated by the flare flux because of its limited bandwidth, but it is sensitive to the arrival of Solar Energetic Particles (SEP). While both channels detect nearly equal SEP fluxes, their contributions to the count rate is sensibly negligible in the zero order channel but must be accounted for and removed from the first channel count rate. SEP contribution to the measured SEM signals usually follows the EUV peak for the gradual solar flare events. Correcting the extreme solar flare SEM EUV measurements may reveal currently unclear relations between the flare magnitude, dynamics observed in different EUV spectral bands, and the measured Earth atmosphere response. A simple and effective correction technique based on analysis of SEM count-rate profiles, GOES X-ray, and GOES proton data has been developed and used for correcting EUV measurements for the five extreme solar flare events of July 14, 2000, October 28, November 2, November 4, 2003, and January 20, 2005. Although none of the 2000 and 2003 flare peaks were contaminated by the presence of SEPs, the January 20, 2005 SEPs were unusually prompt and contaminated the peak. The estimated accuracy of the correction is about 7.5% for large X-class events.

Authors: L.V. Didkovsky (1), D.L. Judge (1), A.R. Jones (1), S. Wieman (1), B.T. Tsurutani (2), and D. McMullin (3)
Projects: None

Publication Status: To appear in Astron. Nachr. / AN, (accepted)
Last Modified: 2006-10-04 13:28
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 

Measuring proton energies and fluxes using EIT (SOHO) CCD areas outside the solar disk images  

Leonid Didkovsky   Submitted: 2006-04-20 11:03

An indirect proton flux measuring tool based on discrimination of the energy deposited by protons in 128 x 128 pixel EIT CCD areas outside the solar disk images is presented. Single pixel intensity events are converted into proton incident energy flux using modeled energy deposition curves for angles of incidence 60 deg in four EIT spatial areas with different proton stopping power. The extracted proton flux is corrected for both the loss of one-pixel events in the range of angles of incidence as well as for the contribution to the single pixel events resulting from scattered middle-energy protons (low-energy or high-energy particles are stopped by the EIT components or pass through them, accordingly). A simple geometrical approach was found and applied to correct for a non-unique relation between the proton-associated CCD output signal and the incident proton energy. With this geometrical approximation four unique proton incident energy ranges were determined as 45-49, 145-154, 297-335, and 390-440 MeV. The indirect proton flux measuring tool has been tested by comparing Solar Energetic Particles (SEP) flux temporal profiles extracted from the EIT CCD frames and downloaded from the GOES database for the Bastille Day (BD) of 2000 July 14 and the more recent 2005 January 20 events. The SEP flux temporal profiles and proton spectra extracted from the EIT in the relatively narrow energy ranges between 45 and 440 MeV reported here are consistent with the related GOES profiles. The four additional EIT extracted ranges provide higher energy resolution of the SEP data.

Authors: L.V. Didkovsky, D.L. Judge, A.R. Jones, E.J. Rhodes, Jr., J.B. Gurman
Projects: SoHO-EIT

Publication Status: published (Astron Nachr. / AN 327, No.4, 314-320 (2006)
Last Modified: 2006-04-24 14:29
Go to main E-Print page  Edit Entry  Download Preprint  Submitter's Homepage Delete Entry 


Key
Go to main E-Print pageGo to main E-Print page.
Download PreprintDownload Preprint.
Submitter's HomepageSubmitters Homepage.
Edit EntryEdit Entry.
Delete AbstractDelete abstract.

Abstracts by Author
Minima of Solar Cycles 22/23 and 23/24 as Seen in SOHO/CELIAS/SEM Absolute Solar EUV Flux
EUV SpectroPhotometer (ESP) in Extreme Ultraviolet Variability Experiment
Correction of SOHO CELIAS/SEM EUV Measurements saturated by extreme solar flare events
Measuring proton energies and fluxes using EIT (SOHO) CCD areas outside the solar disk images

Related Pages
MSU Solar Physics.
Max Millennium Science Mail Archive.
Max Millennium Message of the Day Mail Archive.
Max Millennium Flare Catalog

Archive Maintainer
Alisdair Davey



© 2003 Solar Physics Group - Montana State University