Solar modulation of cosmic ray electrons and positrons measured by the PAMELA experiment during the 23rd solar minimum.

Cosmic rays (CRs) are energetic particles mainly originating outside the Solar System in extremely powerful environments like supernovae remnants (SNRs). The cosmic radiation is composed primarily of high-energy protons, helium and atomic nuclei while only a small fraction are electrons, anti-protons and positrons. During propagation through the Galaxy, CRs interact with the interstellar matter and the Galactic magnetic field. Because of these interactions CRs lose energy and change their spectral features with respect to the injection spectrum. Moreover, before reaching the Earth, CRs traverse the heliosphere, a region of space formed by the continuously outward expanding solar wind. Propagation inside the solar environment make the CR spectra decrease in intensity and vary with time following the 11-year solar cycle. During solar minimum the intensity of CRs on Earth is maximum; the situation reverses during solar maximum. Above 30 GeV the effects of solar modulation are negligible. In this work a new measurement of the time dependent Galactic CR positron and electron energy spectra between 70 MeV and 50 GeV is presented. The analysis was conducted on data collected by the space borne PAMELA experiment during the period from July 2006 to January 2009. This was a period of intense solar minimum and negative solar magnetic field polarity. Long flight duration together with high proton rejection power make the PAMELA instrument the ideal apparatus for measuring the long-term variation of CR electrons and positrons. A total of seven spectra was obtained, each measures over six months period. This solution was a compromise between the time resolution and the statistics. Precise measurement of the electron and positron spectra allows to test the numerical 3D models which describe the transport of charged particles through the heliosphere. The results discussed in this thesis are relevant since they provide long-term observation of electron and positron spectra improving both time resolution and statistical precision with respect to previous experiments. Moreover the measurement is performed down to 70 MeV, an energy region not achievable by other space-borne experiments able to perform charge sign separation like AMS-02. A big effort has been invested to achieve precise results below 200 MeV since a change in the spectral shape is expected from the propagation models. Finally, the simultaneous measure of the positron and electron spectra allow a comprehensive study of the charge-sign dependent modulation of CRs

Osservazione dei raggi cosmici dallo spazio

I raggi cosmici sono particelle energetiche con origine sia nel nostro sistema solare e galassia ma anche fuori della galassia. I raggi cosmici sono in gran parte protoni e nuclei di elio ma sono presenti tutti i nuclei della tavola periodica oltre ad elettroni ed antiparticelle. La loro origine, i processi di accelerazione ad alte energie come pure la propagazione verso la terra sono argomenti che stanno impegnando gli scienziati dalla loro scoperta da parte di Victor Hess nel 1912. Per studiarli adeguatamente è necessario misurarne con precisione lo spettro energetico e la composizione. Queste ricerca è stata, ed è, affrontata sperimentalmente sia con strumentazione a terra che con apparati al sommo dell'atmosfera installati su palloni stratosferici o in satelliti o stazioni spaziali. Quest'ultimo campo ha visto una significativa attività negli ultimi decenni con molti apparati equipaggiati con strumentazione all'avanguardia che hanno prodotto importanti risulti rivoluzionando la comprensione della fisica dei raggi cosmici

Osservazione dei raggi cosmici dallo spazio

I raggi cosmici sono particelle energetiche con origine sia nel nostro sistema solare e galassia ma anche fuori della galassia. I raggi cosmici sono in gran parte protoni e nuclei di elio ma sono presenti tutti i nuclei della tavola periodica oltre ad elettroni ed antiparticelle. La loro origine, i processi di accelerazione ad alte energie come pure la propagazione verso la terra sono argomenti che stanno impegnando gli scienziati dalla loro scoperta da parte di Victor Hess nel 1912. Per studiarli adeguatamente è necessario misurarne con precisione lo spettro energetico e la composizione. Queste ricerca è stata, ed è, affrontata sperimentalmente sia con strumentazione a terra che con apparati al sommo dell'atmosfera installati su palloni stratosferici o in satelliti o stazioni spaziali. Quest'ultimo campo ha visto una significativa attività negli ultimi decenni con molti apparati equipaggiati con strumentazione all'avanguardia che hanno prodotto importanti risulti rivoluzionando la comprensione della fisica dei raggi cosmici

The large area detector onboard the eXTP mission

The Large Area Detector (LAD) is the high-throughput, spectral-timing instrument onboard the eXTP mission, a flagship mission of the Chinese Academy of Sciences and the China National Space Administration, with a large European participation coordinated by Italy and Spain. The eXTP mission is currently performing its phase B study, with a target launch at the end-2027. The eXTP scientific payload includes four instruments (SFA, PFA, LAD and WFM) offering unprecedented simultaneous wide-band X-ray timing and polarimetry sensitivity. The LAD instrument is based on the design originally proposed for the LOFT mission. It envisages a deployed 3.2 m2 effective area in the 2-30 keV energy range, achieved through the technology of the large-area Silicon Drift Detectors - offering a spectral resolution of up to 200 eV FWHM at 6 keV - and of capillary plate collimators - limiting the field of view to about 1 degree. In this paper we will provide an overview of the LAD instrument design, its current status of development and anticipated performance

Isotope solar modulation with the PAMELA experiment.

The satellite-borne PAMELA experiment was launched on the 15th June 2006 from the Baikonur cosmodrome. Since then and until January 2016 PAMELA made high-precision measurements of the charged component of cosmic-rays over a wide energy range. Because of its long-duration operation, PAMELA represents an ideal detector for cosmic-ray solar modulation studies. The PAMELA collaboration already published time-dependent proton, helium and electron spectra as well as the positron to electron ratio over ten years of data taking. These results are fundamental to improve and refine propagation models the propagation models of cosmic rays through the heliosphere. Here, the yearly average spectra over the 23rd solar minimum (July 2006 - January 2009) until the middle of the 24rd solar maximum (December 2015) for 1H, 2H, 3He and 4He are presented. The isotopic composition was measured between 0.1 and 1.1 GeV/n using two different detector systems. These spectra show an increasing trend during the solar minimum period with a decrease as the solar maximum is approached. The time-dependent ratio of these isotopes is also presented. From a solar modulation point of view, a non constant ratio is typically caused by their different masses (related to their rigidity) and also the different shapes of the respective local interstellar spectra. Apart from these effects, it is worthwhile to look deeper for more fundamental causes related to their propagation and modulation mechanisms

The wide field monitor onboard the Chinese-European x-ray mission eXTP

The eXTP (enhanced X-ray Timing and Polarimetry) mission is a major project of the Chinese Academy of Sciences (CAS), with a large involvement of Europe. The scientific payload of eXTP includes four instruments: the SFA (Spectroscopy Focusing Array) and the PFA (Polarimetry Focusing Array) - led by China - the LAD (Large Area Detector) and the WFM (Wide Field Monitor) - led by Europe (Italy and Spain). They offer a unique simultaneous wide-band X-ray timing and polarimetry sensitivity. The WFM is a wide field X-ray monitor instrument in the 2-50 keV energy range, consisting of an array of six coded mask cameras with a field of view of 180ºx90ºat an angular resolution of 5 arcmin and 4 silicon drift detectors in each camera. Its unprecedented combination of large field of view and imaging down to 2 keV will allow eXTP to make important discoveries of the variable and transient X-ray sky and is essential in detecting transient black holes, that are part of the primary science goals of eXTP, so that they can be promptly followed up with other instruments on eXTP and elsewhere

The wide field monitor (WFM) of the China-Europe eXTP (enhanced x-ray timing and polarimetry) mission

The eXTP (enhanced X-ray Timing and Polarimetry) mission is a major project of the Chinese Academy of Sciences (CAS), with a large involvement of Europe. Its scientific payload includes four instruments: SFA (Spectroscopy Focusing Array), PFA (Polarimetry Focusing Array), LAD (Large Area Detector) and WFM (Wide Field Monitor). They offer an unprecedented simultaneous wide-band Xray timing and polarimetry sensitivity. A large European consortium is contributing to the eXTP study, both for the science and the instrumentation. Europe is expected to provide two of the four instruments: LAD and WFM; the LAD is led by Italy and the WFM by Spain. The WFM for eXTP is based on the design originally proposed for the LOFT ESA M3 mission, that underwent a Phase A feasibility study. It will be a wide field of view X-ray monitor instrument working in the 2-50 keV energy range, achieved with large-area Silicon Drift Detectors (SDDs), similar to the ones used for the LAD but with better spatial resolution. The WFM will consist of 3 pairs of coded mask cameras with a total combined field of view (FoV) of 90x180 degrees at zero response and a source localisation accuracy of ~1 arc min. The main goal of the WFM onboard eXTP is to provide triggers for the target of opportunity observations of the narrow field of view instruments (SFA, PFA and LAD), in order to perform the core science observation programme, dedicated to the study of matter under extreme conditions of density, gravity and magnetism. In addition, the unprecedented combination of large field of view and imaging capability, down to 2 keV, of the WFM will allow eXTP to make important discoveries of the variable and transient X-ray sky, and provide X-ray coverage of a broad range of astrophysical objects covered under 'observatory science', such as gamma-ray bursts, fast radio bursts, gravitational wave electromagnetic counterparts. In this paper we provide an overview of the WFM instrument, explaining its design, configuration, and anticipated performance. Right now, eXTP is in phase B2, after a successful I-SRR (Instrument System Requirements Review). It is waiting for the adoption of the whole eXTP mission in China. Details about the current work in Phase B2, including the manufacturing and testing of the demonstration models of the WFM subsystems, will be presented, paying also a special emphasis on the collaboration with space dedicated industrial partners

Effect of the Jupiter magnetosphere on the cosmic ray protons measured with the PAMELA experiment

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