Comparative data quality assessment for ACE SIS, ACE EPAM, WIND 3DP, SOHO/ERNE, and SOHO EPHIN during selected solar energetic particle events

B. Heber1, N. Dresing1, P. Kühl1, R. Gomez-Herrero2, O. Malandraki3, A. Papaioannou3, P. Marhavilas4, E. Valtonen5, O. Raukunen5, V. Riihonen5, and D. Heynderickx6

Abstract: Significant developments in our understanding of energetic particles in the heliosphere are based on both theoretical understanding and observational evidence especially due to more-detailed near-Earth observations. Thus, in anticipation of this network of spacecraft near Earth close to the Langragian point L1, it is a perfect time to develop techniques and strategies for combining the different energetic particle measurements. Different instrumentation measure the energy spectra and pitch angle distribution of ions from a few tenth of keV/nucleon to several hundred of MeV/nucleon as well as electrons in the range from below 20 keV to above 10 MeV. Among other SEPServer was an EU funded project that provides data and a data comparison of ACE SIS, ACE EPAM, WIND 3DP, SOHO/ERNE, SOHO EPHIN and partially STEREO SEPT. The Comparisons were undertaken for selected sample of events. In some cases not only the intensity time profiles but higher order data products such as energy spectra or pitch angle distributions of different instruments were investigated. The results for the November 1997, May 1999, November 2004, July, 2005, January 2007 and May 2007 events will be presented.

1Christian-Albrechts-Universität zu Kiel, Germany, 2Universidad de Alcalá, Departamento de Física y Matemáticas, Spain, 3IAASARS, National Observatory of Athens, Greece, 4Democritus University of Thrace, Greece 5University of Turku, Finnland,6DH Consultancy, Belgium

Acknowledgements:The SEPServer consortium gratefully acknowledges the financial support of the European Union through its Seventh Framework Program (FP7-SPACE), Grant Agreement # 262773. The consortium is also grateful to the PIs providing their data to the project.

Introduction

SEPServer (www.sepserver.eu) is a collaborative project of eleven European partners funded by the European Union’s Seventh Framework Programme. The project was launched in December 2010 and was running for three years. The main objective of the project is to develop an Internet server facilitating access to solar energetic particle (SEP) data and related electromagnetic observations and to browsing tools and state-of-the-art analysis methods. The database contains SEP observations from a number of spacecraft at L1 and from HELIOS, Ulysses and STEREO. The project has performed an analysis of the SEP events observed by several spacecraft and provide these results to the community in form of event catalogs (Vainio et al, 2013, Papaioannou et al., 2014). Comparisons of the data delivered to SEPServer are undertaken for selected sample of events. In some cases not only the intensity time profiles but higher order data products such as energy spectra or pitch angle distributions of different instruments are compared with each other. Of special interest to the project are the data sets close to Earth and at a distance of about 1 AU.

References:1.Papaioannou, A. et al., 2014. SEPServer STEREO Catalogues of Solar Energetic Particle Events at 1 AU based on STEREO recordings: 2007-2012, Astron. Astrophys., 569, A96, doi: 10.1051/0004-6361/2013233362.Vainio, R. et al., 2013. The first SEPServer event catalogue ~68-MeV solar proton events observed at 1 AU in 1996-2010. Journal of Space Weather and Space Climate, 3, p.12.

Instrumentation

Results

Proton and helium observations in four solar energetic particle events by various instruments close to 1 AU were compared. The selection included different sizes of events. Intensity-time profiles of protons for WIND/3DP, ACE/EPAM, SOHO/EPHIN and SOHO/ERNE were presented to demonstrate that all four instruments were able to record the events. The energy spectra of protons from ACE/EPAM, SOHO/EPHIN and SOHO/ERNE covered an energy range of more than three orders of magnitude (70 keV - >100 MeV), while the energy spectra of helium from ACE/SIS, SOHO/EPHIN and SOHO/ERNE extended over roughly two orders of magnitude ( 1 MeV/nucleon – 100 MeV/nucleon). In all cases the agreement between different instruments was reasonably good taking into account the slightly different locations of the spacecraft. However, a rapid fall of the proton and helium spectra measured by SOHO/ERNE was observed at the highest energies ( 80 MeV/nucleon), which cannot be readily explained.≳

Electron measurements of ACE/EPAM and WIND/3DP were compared for the SEP event of February 18, 2000. The agreement of the electron energy spectra of WIND/3DP and ACE/EPAM was found to be very good.

Poster id 72832

The following events were selected for the comparision between ACE SIS, ACE EPAM, WIND 3DP, SOHO/ERNE (see talk by Valtonen et al.), and SOHO EPHIN:

1.13 November 1997, event number 4 of the SOHO/ERNE event list. 2.27 May 1999, event number 17 of the SOHO/ERNE event list. 3.01 November 2004, event number 96 of the SOHO/ERNE event list. 4.14 July, 2005, event number 105 of the SOHO/ERNE event list.

Time profiles and the energy spectra of protons and alpha-particles for the July 13, 2005 event measured by SOHO/ERNE, SOHO/EPHIN ACE/SIS and ACE/EPAM The agreement for protons and alpha particles is very good over the entire common energy range of the instruments.

The February 18, 2000 event (electrons)

dE/dx-E: SIS, EPHIN, ERNE

Magnet-Foil system: 3DP, EPAM

1999 2005

July 13/14, 2005 solar energetic particle event

The comparison of the electrons are derived by http://plasma2.ssl.berkeley.edu/~krucker/ace/epam_3dp.html