Speaker
Description
The publicly available data of the Energetic and Relativistic Nuclei and electron Experiment (ERNE) aboard the Solar and Heliospheric Observatory (SOHO) currently extends to ∼100 MeV for protons. However, the instrument has some channels that primarily respond to high-energy protons (hundreds of MeVs) that have so far neither been calibrated nor released. Within the EU Horizon Europe project SPEARHEAD (SPEcification, Analysis & Re-calibration of High Energy pArticle Data), the Geant4 model of the instrument has been reconstructed using the paper drawings archive, and its response functions have been recalculated.
Penetrating particles in the detector are identified by detecting a signal in the plastic scintillator anti-coincidence (AC) detector in the bottom of the detector stack. The detector is read out by photodiodes instead of photomultipliers, which leads to a non-ideal detection efficiency of penetrating particles. As there is no pulse-height data available from the scintillator, and the detection threshold was not calibrated prior to the launch, the threshold of the ERNE AC counters is not well known. Because without knowledge of this threshold real physical quantities cannot be obtained from the ERNE observations, an in-flight calibration of the detection threshold has been attempted, taking advantage of the fact that with the Electron Proton Helium INstrument (EPHIN) another detector is aboard SOHO that provides reliable observations of protons in the same energy range. With a subsequent bow-tie analysis, the effective energy (~130 MeV) and differential geometric factor (~878 cm2) of this previously unused instrument channel can be determined. Here, we provide an overview of the work done so far and give an outlook on the ongoing efforts that are foreseen to result in a new dataset of ~130 MeV proton observations over the whole SOHO mission period of almost 30 years.
SPEARHEAD has received funding from the European Union’s Horizon Europe programme under grant agreement No 101135044. The work reflect only the authors’ view, and the European Commission is not responsible for any use that may be made of the information it contains.
