scholarly journals Evolution of the Solar Magnetic Activity over Time and Effects on Planetary Atmospheres

2004 ◽  
Vol 219 ◽  
pp. 423-430 ◽  
Author(s):  
Edward F. Guinan ◽  
Ignasi Ribas
Keyword(s):  
Solar System ◽  
High Energy ◽  
Planetary Atmospheres ◽  
Magnetic Activity ◽  
Spectral Irradiance ◽  
X Rays ◽  
Early Solar System ◽  
Particle Emissions ◽  
Multi Wavelength ◽  
Energy Emissions

We report on the results of a multi-wavelength program (X-rays to the near IR) of solar analogs with ages covering ∼0.1—9 Gyr. The chief science goals are to study the solar magnetic dynamo and to determine the radiative and magnetic properties of the Sun during its evolution across the main sequence. The present paper focuses on the latter goal, which has the ultimate purpose of constructing spectral irradiance tables to be used to study and model planetary atmospheres. The results obtained thus far indicate that the young Sun was extremely active, with large flares, massive winds, and high-energy emissions up to 1000 times stronger than presently. The strong radiation and particle emissions inferred should have had major influences on the photochemistry and photo-ionization of paleo-planetary atmospheres and also played an important role in the development of primitive life in the Solar System. Some recent results of the effects of the young Sun's enhanced radiation and particle emissions on the early Solar System planets are discussed.

scholarly journals The Sun in time: age, rotation, and magnetic activity of the Sun and solar-type stars and effects on hosted planets

2008 ◽  
Vol 4 (S258) ◽  
pp. 395-408 ◽  
Author(s):  
Edward F. Guinan ◽  
Scott G. Engle
Keyword(s):  
Main Sequence ◽  
High Energy ◽  
Magnetic Activity ◽  
The Sun ◽  
X Ray ◽  
Multi Wavelength ◽  
Solar Type ◽  
Rotation Age ◽  
Energy Emissions ◽  
Solar Analogs

AbstractMulti-wavelength studies of solar analogs (G0–5 V stars) with ages from ~50 Myr to 9 Gyr have been carried out as part of the “Sun in Time” program for nearly 20 yrs. From these studies it is inferred that the young (ZAMS) Sun was rotating more than 10× faster than today. As a consequence, young solar-type stars and the early Sun have vigorous magnetohydrodynamic (MHD) dynamos and correspondingly strong coronal X-ray and transition region/chromospheric FUV–UV emissions (up to several hundred times stronger than the present Sun). Also, rotational modulated, low amplitude light variations of young solar analogs indicate the presence of large starspot regions covering ~5–30% of their surfaces. To ensure continuity and homogeneity for this program, we use a restricted sample of G0–5 V stars with masses, radii, Teff, and internal structure (i.e. outer convective zones) closely matching those of the Sun. From these analogs we have determined reliable rotation-age-activity relations and X-ray–UV (XUV) spectral irradiances for the Sun (or any solar-type star) over time. These XUV irradiance measures serve as input data for investigating the photo-ionization and photo-chemical effects of the young, active Sun on the paleo-planetary atmospheres and environments of solar system planets. These measures are also important to study the effects of these high energy emissions on the numerous exoplanets hosted by solar-type stars of different ages. Recently we have extended the study to include lower mass, main-sequence (dwarf) dK and dM stars to determine relationships among their rotation spin-down rates and coronal and chromospheric emissions as a function of mass and age. From rotation-age-activity relations we can determine reliable ages for main-sequence G, K, M field stars and, subsequently, their hosted planets. Also inferred are the present and the past XUV irradiance and plasma flux exposures that these planets have endured and the suitability of the hosted planets to develop and sustain life.

scholarly journals The Sun and stars as the primary energy input in planetary atmospheres

2009 ◽  
Vol 5 (S264) ◽  
pp. 3-18 ◽  
Author(s):  
Ignasi Ribas
Keyword(s):  
Planetary Atmospheres ◽  
Primary Energy ◽  
Stellar Atmospheres ◽  
Structure Evolution ◽  
Strong Impact ◽  
The Sun ◽  
X Rays ◽  
Low Mass Stars ◽  
Particle Emissions ◽  
Mere Existence

AbstractProper characterization of the host star to a planet is a key element to the understanding of its overall properties. The star has a direct impact through the modification of the structure and evolution of the planet atmosphere by being the overwhelmingly larger source of energy. The star plays a central role in shaping the structure, evolution, and even determining the mere existence of planetary atmospheres. The vast majority of the stellar flux is well understood thanks to the impressive progress made in the modeling of stellar atmospheres. At short wavelengths (X-rays to UV), however, the information is scarcer since the stellar emission does not originate in the photosphere but in the chromospheric and coronal regions, which are much less understood. The same can be said about particle emissions, with a strong impact on planetary atmospheres, because a detailed description of the time-evolution of stellar wind is still lacking. Here we review our current understanding of the flux and particle emissions of the Sun and low-mass stars and briefly address their impact in the context of planetary atmospheres.

High-energy radiation from natural lightning observed in coincidence with a VHF Lightning Interferometer

2020 ◽  
Author(s):  
Michele Urbani ◽  
Joan Montanyà ◽  
Oscar Van der Velde ◽  
Jesús Alberto López
Keyword(s):  
High Energy ◽  
Strong Absorption ◽  
X Rays ◽  
Coverage Area ◽  
Radiation Mechanism ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
X Ray ◽  
Cloud To Ground Lightning ◽  
Energy Emissions

<p>In the last two decades, it has been discovered that lightning strikes can emit high-energy radiation.<br>In particular, a phenomenon has been observed from space called "Terrestrial Gamma-ray Flash'' (TGF), which consists of an intense burst of gamma radiation that can be produced during thunderstorms. This phenomenon has met with considerable interest in the scientific community and its mechanism is still not fully understood. Nowadays several satellites for astrophysics like AGILE and FERMI are able to detect and map TGFs and specific instruments like the ASIM detector on the ISS are studying this phenomenon from space.<br>In the atmosphere, the high-energy radiation undergoes a strong absorption exponentially proportional to the air density which makes it more difficult to detect TGFs on the ground. Nonetheless, ground measurements were conducted and observed that even in cloud-to-ground lightning high-energy radiation were produced. In particular, the works of Moore et al. [2001] and Dwyer et al. [2005] highlight two lightning processes in which the X-ray emission could be produced: downward negative stepped leader and dart leader. Currently, it is not clear if the emissions revealed on the ground and the TGFs observed in space are essentially the same phenomenon or how these phenomena are related. For these reasons, it is particularly interesting to study high-energy emissions also from ground instruments because, despite the strong absorption of the high-energy radiation, ground observations can reach a better accuracy in time and space and provide crucial information to investigate the origin and conditions under which these emissions occur.<br>A privileged instrument for this research is the VHF Lightning Interferometer, a system of antennas that allows you to map lightning through the very high frequency (VHF) emission. Due to the high resolution of this instrument, should be possible to locate the origin of the high-energy emissions and hopefully provide a better understanding of the radiation mechanism.<br>The aim of this research is, therefore, to develop a 3D interferometry system to identify as accurately as possible the origin and the conditions in which the X-ray emission occurs in cloud-to-ground lightning and investigate the relation of the VHF emissions with the TGFs.<br>Recently an observation campaign was conducted in Colombia with two VHF Lightning Interferometers and two X-rays detectors. This interferometry system was installed in the coverage area of a Lightning Mapping Array (LMA) and LINET to take advantage of the complementary information that these lightning location networks could provide. At the moment, about 15 lightning events with X-ray emissions were observed, including five X-ray bursts from downward negative leaders and two emissions from dart leaders. Further studies and analysis of the collected data are still ongoing.</p>

Multi-wavelength anomalous diffraction method for I and Xe atoms using ultra-high-energy X-rays from SPring-8

2004 ◽  
Vol 37 (6) ◽  
pp. 925-933 ◽  
Author(s):  
Kazuki Takeda ◽  
Hideyuki Miyatake ◽  
Sam-Yong Park ◽  
Masahide Kawamoto ◽  
Nobuo Kamiya ◽  
...  
Keyword(s):  
Diffraction Method ◽  
High Energy ◽  
X Rays ◽  
Ultra High Energy ◽  
Anomalous Diffraction ◽  
Egg White Lysozyme ◽  
Density Maps ◽  
Mad Phasing ◽  
Multi Wavelength ◽  
Lysozyme Crystals

The first successful multi-wavelength anomalous diffraction (MAD) experiments using ultra-high-energy X-rays (∼35 keV) were performed for iodine and xenon derivatives of hen egg-white lysozyme crystals. The beamline BL41XU of SPring-8 enabled the collection of high-quality MAD data, which led to the calculation of anomalous or dispersive difference Patterson maps that determined the positions of iodine and xenon atoms. The electron density maps obtained by the density modification method for both cases proved to be of sufficient quality for building molecular models. I-MAD and Xe-MAD phasing are now available at SPring-8, and the utilization of ultra-high-energy X-rays will make a significant contribution to the solution of the phase problem in protein crystallography.

scholarly journals Multi-wavelength Behaviour of III Zw2

2002 ◽  
Vol 19 (1) ◽  
pp. 73-76
Author(s):  
Nikita Salvi ◽  
Mat J. Page ◽  
Jason A. Stevens ◽  
Keith O. Mason ◽  
Kinwah Wu
Keyword(s):  
Synchrotron Radiation ◽  
Optical Emission ◽  
High Energy ◽  
X Rays ◽  
X Ray ◽  
High Energy Electrons ◽  
Photon Index ◽  
Multi Wavelength ◽  
Wavelength Light ◽  
Gaussian Line

AbstractIII Zw2 was observed with XMM-Newton in July 2000. Its X-ray spectrum can be described by a power law of photon index Γ≈1.7 with a Gaussian line at 6.7 KeV. There is no significant evidence of intrinsic absorption within the source or of a soft X-ray excess. Multi-wavelength light curves over a period of 25 years show related variations from the radio to X-rays. We interpret the radio to optical emission as synchrotron radiation, self-absorbed in the radio/millimetre region, and the X-rays as mainly due to Compton up-scattering of low energy photons by the population of high energy electrons that give rise to the synchrotron radiation.

scholarly journals Stellar Coronal Spectroscopy with the Chandra HETGS

2004 ◽  
Vol 219 ◽  
pp. 238-242 ◽  
Author(s):  
David P. Huenemoerder ◽  
Bram Boroson ◽  
Norbert S. Schulz ◽  
Claude R. Canizares ◽  
Derek L. Buzasi ◽  
...  
Keyword(s):  
High Energy ◽  
Magnetic Activity ◽  
Tauri Star ◽  
X Rays ◽  
Transmission Grating ◽  
Long Period ◽  
Rotational Modulation ◽  
T Tauri ◽  
Long Duration ◽  
Period System

Spectroscopy with the Chandra High Energy Transmission Grating Spectrometer (HETGS) provides details on X-ray emission and activity from young and cool stars through resolution of emission lines from a variety of ions. We are beginning to see trends in activity regarding abundances, emission measures, and variability. Here we contrast spectra of TV Crt, a weak-lined T Tauri star (WTT), with TW Hya, a Classical T Tauri star (CTT). TV Crt has a spectrum more like magnetic activity driven coronae, relative to the TW Hya spectrum, which we have interpreted as due to accretion-produced X-rays. We have also observed the long period system, IM Pegasi to search for rotational modulation, and to compare activity in a long period active binary to shorter period systems and to the pre-main sequence stars. We detected no rotational modulation, but did see long-duration flares.

scholarly journals A fast, very-high-energy γ-ray flare from BL Lacertae during a period of multi-wavelength activity in June 2015

2019 ◽  
Vol 623 ◽  
pp. A175 ◽  
Author(s):  
◽  
V. A. Acciari ◽  
S. Ansoldi ◽  
L. A. Antonelli ◽  
A. Arbet Engels ◽  
...  
Keyword(s):  
Spectral Energy Distribution ◽  
Interaction Model ◽  
High Energy ◽  
Spectral Energy ◽  
Polarization Angle ◽  
X Rays ◽  
Bl Lacertae ◽  
Multi Wavelength ◽  
Very High Energy ◽  
Very High

The mechanisms producing fast variability of the γ-ray emission in active galactic nuclei (AGNs) are under debate. The MAGIC telescopes detected a fast, very-high-energy (VHE, E  >  100 GeV) γ-ray flare from BL Lacertae on 2015 June 15. The flare had a maximum flux of (1.5 ± 0.3) × 10−10 photons cm−2 s−1 and halving time of 26 ± 8 min. The MAGIC observations were triggered by a high state in the optical and high-energy (HE, E  >  100 MeV) γ-ray bands. In this paper we present the MAGIC VHE γ-ray data together with multi-wavelength data from radio, optical, X-rays, and HE γ rays from 2015 May 1 to July 31. Well-sampled multi-wavelength data allow us to study the variability in detail and compare it to the other epochs when fast, VHE γ-ray flares have been detected from this source. Interestingly, we find that the behaviour in radio, optical, X-rays, and HE γ-rays is very similar to two other observed VHE γ-ray flares. In particular, also during this flare there was an indication of rotation of the optical polarization angle and of activity at the 43 GHz core. These repeating patterns indicate a connection between the three events. We also test modelling of the spectral energy distribution based on constraints from the light curves and VLBA observations, with two different geometrical setups of two-zone inverse Compton models. In addition we model the γ-ray data with the star-jet interaction model. We find that all of the tested emission models are compatible with the fast VHE γ-ray flare, but all have some tension with the multi-wavelength observations.

scholarly journals EUV irradiation of exoplanet atmospheres occurs on Gyr time-scales

2020 ◽  
Vol 501 (1) ◽  
pp. L28-L32
Author(s):  
George W King ◽  
Peter J Wheatley
Keyword(s):  
Mass Loss ◽  
Time Scales ◽  
High Energy ◽  
Planetary Atmospheres ◽  
X Rays ◽  
X Ray ◽  
Atmospheric Escape ◽  
Euv Emission ◽  
Energy Emission ◽  
High Energy Emission

ABSTRACT Exoplanet atmospheres are known to be vulnerable to mass-loss through irradiation by stellar X-ray and extreme-ultraviolet (EUV) emission. We investigate how this high-energy irradiation varies with time by combining an empirical relation describing stellar X-ray emission with a second relation describing the ratio of solar X-ray to EUV emission. In contrast to assumptions commonly made when modelling atmospheric escape, we find that the decline in stellar EUV emission is much slower than in X-rays, and that the total EUV irradiation of planetary atmospheres is dominated by emission after the saturated phase of high-energy emission (which lasts around 100 Myr after the formation of the star). The EUV spectrum also becomes much softer during this slow decline. Furthermore, we find that the total combined X-ray and EUV emission of stars occurs mostly after the saturated phase. Our results suggest that models of atmospheric escape that focus on the saturated phase of high-energy emission are oversimplified, and when considering the evolution of planetary atmospheres it is necessary to follow EUV-driven escape on Gyr time-scales. This may make it more difficult to use stellar age to separate the effects of photoevaporation and core-powered mass-loss when considering the origin of the planet radius valley.

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