Paul A. Evenson

The University of Chicago Cosmic Ray Electrons and Nuclei Experiment on the H Spacecraft

The University of Chicago instrument on the Heliocentric spacecraft (MEH experiment) will measure the energy spectrum of cosmic electrons in the range 5-400 MeV. In addition, the energy spectra and relative abundances of nuclei from protons to the iron group, with energies ranging from 30 MeV/n to 15 GeV/n, will be determined. Primary scientific objectives involve the study of the long and short term variability of these components as a probe of the structure of the heliosphere. Particles are identified by multiparameter analysis using the pulse height analized signals from eight active detectors-silicon solid state, plastic and crystal scintillators are solid and gas Cerenkov counters. Data return is optimized by a three level priority logic scheme.

Tracking cosmic-ray spectral variations with neutron monitor time-delay measurements at high cutoff rigidity during 2007-2017

We present measurements of the leader fraction of neutron monitor counts that did not follow other counts in the same counter tube from the same cosmic ray shower. We use time-delay histograms collected at the Princess Sirindhorn Neutron Monitor at Doi Inthanon, Thailand, which has the worlds highest vertical cutoff rigidity for a fixed station (16.8 GV). Changes in the leader fraction are a precise indicator of cosmic ray spectral variations above the cutoff. Our data set from 2007 to 2017 spans a full cycle of solar modulation, including the all-time cosmic ray maximum of 2009 and minimum near the end of 2014, the count rate now having returned to its initial value. The electronics to collect time-delay histograms have been upgraded twice, and we have corrected for such changes to develop a long-term leader fraction dataset. We examine the spectral variation of Galactic cosmic rays above

A Study on Diurnal Variation of Cosmic Ray Flux using Daejeon and Jang Bogo Neutron Monitors

\sim

Cosmic Ray Modulation Observed by the Princess Sirindhorn Neutron Monitor at High Rigidity Cutoff

17 GV resulting from solar modulation and its solar magnetic polarity dependence.

Impulsive Increase of Galactic Cosmic Ray Flux Observed by IceTop

The diurnal variation of galactic cosmic ray flux measured by ground base neutron monitor stations. The local time of maximum intensity tends to depending on latitudinal location. Depending on solar activity, drift effect and diffusion effect controls the local time of maximum intensity for cosmic ray flux. The drift effect occurs due to solar magnetic reversal and the diffusion effect occur due to change in the interplanetary magnetic field scales related to the sunspot cycle. Recently, we installed cosmic ray neutron monitor at Daejeon in south Korea (October 2011) and at Jang Bogo station in Antarctica (December 2015). We want to know the characteristics of two neutron monitors data and adequacy of the data using the local time diurnal variation of cosmic ray flux at two locations and previous studies. We used the plie-up method to analyze diurnal variation for these two stations and used the data from January 1, 2016 to December 31, 2016. In this report, we will present results about diurnal variation of cosmic ray flux at Daejeon neutron monitor and Jang Bogo neutron monitor. This results will tell us if there are good values for the neutron monitor stations.

High-energy cosmic ray modulation associated with interplanetary shocks observed by the GMDN

Solar modulation refers to Galactic cosmic ray (GCR) variations with the

Average features of the interplanetary shock observed with the Global Muon Detector Network (GMDN)

\sim

Cosmic Ray Electron Spectrum in 2009

11-year sunspot cycle and

The Dependence of Solar Modulation on the Sign of the Cosmic Ray Particle Charge during the 22-year Solar Magnetic Cycle

\sim

Precursors to Forbush Decreases and Space Weather Prediction

22-year solar magnetic cycle, and is relevant to the space radiation environment and effects on Earths atmosphere. Its complicated dependence on solar and heliospheric conditions is only roughly understood but has been empirically modeled in terms of a single modulation parameter. Most analyses of solar modulation used neutron monitor (NM) data from locations with relatively low geomagnetic cutoff rigidity, i.e., the threshold for cosmic rays to penetrate Earths magnetic field. The Princess Sirindhorn Neutron Monitor (PSNM) at Doi Inthanon, Thailand has the highest cutoff rigidity (