Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMuon excess at sea level from solar flares in association with the Fermi GBM spacecraft detector
96
0
0.0
(
0
)
Added by
Carlos Navia C. navia
Publication date
2010
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
This paper presents results of an ongoing survey on the associations between muon excesses at ground level registered by the Tupi telescopes and transient solar events, two solar flares whose gamma-ray and X-ray emissions were reported by, respectively, the Fermi GBM and the GOES 14. We show that solar flares of small scale, those with prompt X-ray emission classified by GOES as C-Class (power $10^{-6}$ to $10^{-5}$ W m$^2$ at 1 AU) may give rise to muon excess probably associated with solar protons and ions emitted by the flare and arriving at the Earth as a coherent particle pulse. The Tupi telescopes are within the central region of the South Atlantic Anomaly (SAA), which allows particle detectors to achieve a low rigidity of response to primary and secondary charged particles ($geq 0.1$ GV). Here we argue for the possibility of a scale-free energy distribution of particles accelerated by solar flares. Large and small scale flares have the same energy spectrum up to energies exceeding the pion production, the difference between them is only the intensity. If this hypothesis is correct, the Tupi telescope is registering muons produced by protons (ions) whose energy corresponds to the tail of the spectrum. Consequently the energy distribution of the emitted protons has to be a power law spectrum, since power law distributions are characterized as scale free distributions. The Tupi events give support to this conjecture.
rate research
Read More
Using two years of data from the NOvA Near Detector at Fermilab, we report a seasonal variation of cosmic ray induced multiple-muon event rates which has an opposite phase to the seasonal variation in the atmospheric temperature. The strength of the seasonal multipl$ increase as a function of the muon multiplicity. However, no significant dependence of the strength of the seasonal variation of the multiple-muon variation is seen as a function of the muon zenith angle, or the spatial or angular separation between the correlated muons.
The Kepler space telescope yielded unprecedented data for the study of solar-like oscillations in other stars. The large samples of multi-year observations posed an enormous data analysis challenge that has only recently been surmounted. Asteroseismic modeling has become more sophisticated over time, with better methods gradually developing alongside the extended observations and improved data analysis techniques. We apply the latest version of the Asteroseismic Modeling Portal (AMP) to the full-length Kepler data sets for 57 stars and the Sun, comprising planetary hosts, binaries, solar-analogs, and active stars. From an analysis of the derived stellar properties for the full sample, we identify a variation of the mixing-length parameter with atmospheric properties. We also derive a linear relation between the stellar age and a characteristic frequency separation ratio. In addition, we find that the empirical correction for surface effects suggested by Kjeldsen and coworkers is adequate for solar-type stars that are not much hotter (Teff < 6200 K) or significantly more evolved (logg > 4.2, <Delta_nu> > 80 muHz) than the Sun. Precise parallaxes from the Gaia mission and future observations from TESS and PLATO promise to improve the reliability of stellar properties derived from asteroseismology.
The heliospheric magnetic field (HMF) is structured into large sectors of positive and negative polarity. The parts of the boundary between these sectors where the change in polarity matches that of the leading-to-following sunspot polarity in that solar hemisphere, are called Hale Sector Boundaries (HSB). We investigate the flare occurrence rate near HSBs and the association between HSBs and active longitudes. Previous work determined the times HSBs were at solar central meridian, using the detection of the HMF sector boundary crossing at the Earth. In addition to this, we use a new approach which finds the HSB locations at all times by determining them from Potential Field Source Surface (PFSS) extrapolations of photospheric magnetograms. We use the RHESSI X-ray flare list for comparison to the HSB as it provides accurate flare locations over 14 years, from February 2002 to February 2016, covering both Cycles 23 and 24. For the active longitude positions we use previously published work based on sunspot observations. We find that the two methods of determining the HSB generally agree and that 41% (Cycle 23) and 47% (Cycle 24) of RHESSI flares occur within $30^circ$ of the PFSS determined-HSB. The behaviour of the HSBs varies over the two Cycles studied, and as expected they swap in hemisphere as the Cycles change. The HSBs and active longitudes do overlap but not consistently. They often move at different rates relative to each other (and the Carrington solar rotation rate) and these vary over each Cycle. The HSBs provide a useful additional activity indicator, particularly during periods when active longitudes are difficult to determine.
We report on two millimeter flares detected by ALMA at 220 GHz from AU Mic, a nearby M dwarf. The larger flare had a duration of only $sim35$ sec, with peak $L_{R}=2times10^{15}$ erg s$^{-1}$ Hz$^{-1}$, and lower limit on linear polarization of $|Q/I|>0.12pm0.04$. We examine the characteristics common to these new AU Mic events and those from Proxima Cen previously reported in MacGregor et al. (2018) - namely short durations, negative spectral indices, and significant linear polarization - to provide new diagnostics of conditions in outer stellar atmospheres and details of stellar flare particle acceleration. The event rates ($sim20$ and $4$ events day$^{-1}$ for AU Mic and Proxima Cen, respectively) suggest that millimeter flares occur commonly but have been undetected until now. Analysis of the flare observing frequency and consideration of possible incoherent emission mechanisms confirms the presence of MeV electrons in the stellar atmosphere occurring as part of the flare process. The spectral indices point to a hard distribution of electrons. The short durations and lack of pronounced exponential decay in the light curve are consistent with formation in a simple magnetic loop, with radio emission predominating from directly precipitating electrons. We consider the possibility of both synchrotron and gyrosynchrotron emission mechanisms, although synchrotron is favored given the linear polarization signal. This would imply that the emission must be occurring in a low density environment of only modest magnetic field strength. A deeper understanding of this newly discovered and apparently common stellar flare mechanism awaits more observations with better-studied flare components at other wavelengths.
Recently, many superflares on solar-type stars were discovered as white-light flares (WLFs). A correlation between the energies (E) and durations (t) of superflares is derived as $tpropto E^{0.39}$, and this can be theoretically explained by magnetic reconnection ($tpropto E^{1/3}$). In this study, we carried out a statistical research on 50 solar WLFs with SDO/HMI to examine the t-E relation. As a result, the t-E relation on solar WLFs ($tpropto E^{0.38}$) is quite similar stellar superflares, but the durations of stellar superflares are much shorter than those extrapolated from solar WLFs. We present the following two interpretations; (1) in solar flares, the cooling timescale of WL emission may be longer than the reconnection one, and the decay time can be determined by the cooling timescale; (2) the distribution can be understood by applying a scaling law $tpropto E^{1/3}B^{-5/3}$ derived from the magnetic reconnection theory.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
