Chapter 7 Solar and Heliospheric Physics and Interdisciplinary Research with LHAASO

In the following sub-sections, studies of solar-heliospheric effects on cosmic rays, investigating a possible link between cosmic ray flux and Earth’s climate, and detection of MeV-range γ-rays from thunderstorms with the data from LHAASO will be discussed; geophysical research with environmental neutrons will be introduced, and some Monte Carlo simulation results about effects of thunderstorm electric fields on LHAASO observations of cosmic rays will be given.

PeV Emission of the Crab Nebula: Constraints on the Proton Content in Pulsar Wind and Implications

Recently, two photons from the Crab Nebula with energy of approximately 1 PeV were detected by the Large High Altitude Air Shower Observatory (LHAASO), opening an ultrahigh-energy window for studying pulsar wind nebulae (PWNe). Remarkably, the LHAASO spectrum at the highest-energy end shows a possible hardening, which could indicate the presence of a new component. A two-component scenario with a main electron component and a secondary proton component has been proposed to explain the whole spectrum of the Crab Nebula, requiring a proton energy of 1046–1047 erg remaining in the present Crab Nebula. In this paper, we study the energy content of relativistic protons in pulsar winds using the LHAASO data of the Crab Nebula, considering the effect of diffusive escape of relativistic protons. Depending on the extent of the escape of relativistic protons, the total energy of protons lost in the pulsar wind could be 10–100 times larger than that remaining in the nebula presently. We find that the current LHAASO data allow up to (10–50)% of the spindown energy of pulsars being converted into relativistic protons. The escaping protons from PWNe could make a considerable contribution to the cosmic-ray flux of 10–100 PeV. We also discuss the leptonic scenario for the possible spectral hardening at PeV energies.

Constraining positron emission from pulsar populations with AMS-02 data

The cosmic-ray flux of positrons is measured with high precision by the space-borne particle spectrometer AMS-02. The hypothesis that pulsar wind nebulae (PWNe) can significantly contribute to the excess of the positron (e+) cosmic-ray flux has been consolidated after the observation of a γ-ray emission at TeV energies of a few degree size around Geminga and Monogem PWNe. In this work we undertake massive simulations of galactic pulsars populations, adopting different distributions for their position in the Galaxy, intrinsic physical properties, pair emission models, in order to overcome the incompleteness of the ATNF catalog. We fit the e+ AMS-02 data together with a secondary component due to collisions of primary cosmic rays with the interstellar medium. We find that several mock galaxies have a pulsar population able to explain the observed e+ flux, typically by few, bright sources. We determine the physical parameters of the pulsars dominating the e+ flux, and assess the impact of different assumptions on radial distributions, spin-down properties, Galactic propagation scenarios and e+ emission time.

The Regener-Pfotzer Maximum During a Total Solar Eclipse

The Regener-Pfotzer (RP) maximum is the altitude at which cosmic radiation intensity is the greatest. A decrease of the altitude of the interaction layer, assumed to be measured by the RP maximum, has been suggested to account for a reduction in the secondary cosmic ray flux measured at the surface of the Earth during a total solar eclipse. To investigate this suggestion, high altitude cosmic radiation was measured using Geiger Mueller (GM) counters carried beneath weather balloons both before and during the total solar eclipse on 21 August 2017. The 19 and 20 August 2017 omnidirectional RP maxima occurred at an average altitude of 20.2 km ± 0.9 km. During the eclipse of 21 August 2017 the omnidirectional RP maxima occurred at an altitude of 20.4 km ± 0.8 km. The 19 and 20 August 2017 vertical coincidence RP maxima occurred at an altitude of 18.3 km ± 1.0 km. During the eclipse the vertical coincidence RP maxima occurred at 18.0 km ± 1.0 km. Our results do not show any decrease in the altitude of either the omnidirectional or the vertical coincidence RP maximum outside the range of our measurements before the eclipse.

Comparison of long-term variations of the cosmic ray flux from the network of ground-based detectors, PAMELA and AMS-02 data

The paper presents preliminary results of a comparison of long-term variations of the cosmic ray flux using data from the network of ground-based detectors with direct flux measurements on the PAMELA and AMS-02 magnetic spectrometers and a series of balloon stratospheric soundings. The analysis showed good agreement for the entire period of continuous ground-based monitoring of cosmic ray variations.