scholarly journals 3D propagation of relativistic solar protons through interplanetary space

2020 ◽  
Vol 639 ◽  
pp. A105
Author(s):  
S. Dalla ◽  
G. A. de Nolfo ◽  
A. Bruno ◽  
J. Giacalone ◽  
T. Laitinen ◽  
...  
Keyword(s):  
Interplanetary Space ◽  
Traditional Approach ◽  
Ground Level ◽  
Mean Free Path ◽  
Heliospheric Current Sheet ◽  
High Spectral Resolution ◽  
Particle Model ◽  
3D Effects ◽  
Field Lines ◽  
Energy Dependent

Context. Solar energetic particles (SEPs) with energy in the GeV range can propagate to Earth from their acceleration region near the Sun and produce ground level enhancements (GLEs). The traditional approach to interpreting and modelling GLE observations assumes particle propagation which is only parallel to the magnetic field lines of interplanetary space, that is, spatially 1D propagation. Recent measurements by PAMELA have characterised SEP properties at 1 AU for the ∼100 MeV–1 GeV range at high spectral resolution. Aims. We model the transport of GLE-energy solar protons using a 3D approach to assess the effect of the heliospheric current sheet (HCS) and drifts associated to the gradient and curvature of the Parker spiral. We derive 1 AU observables and compare the simulation results with data from PAMELA. Methods. We use a 3D test particle model including a HCS. Monoenergetic populations are studied first to obtain a qualitative picture of propagation patterns and numbers of crossings of the 1 AU sphere. Simulations for power law injection are used to derive intensity profiles and fluence spectra at 1 AU. A simulation for a specific event, GLE 71, is used for comparison purposes with PAMELA data. Results. Spatial patterns of 1 AU crossings and the average number of crossings per particle are strongly influenced by 3D effects, with significant differences between periods of A+ and A− polarities. The decay time constant of 1 AU intensity profiles varies depending on the position of the observer and it is not a simple function of the mean free path as in 1D models. Energy dependent leakage from the injection flux tube is particularly important for GLE energy particles, resulting in a rollover in the spectrum.

scholarly journals Role of the heliospheric current sheet in high energy proton transport through modelling of historic GLE events 

2021 ◽  
Author(s):  
Charlotte Waterfall ◽  
Silvia Dalla
Keyword(s):  
Current Sheet ◽  
Test Particle ◽  
Ground Level ◽  
High Energy ◽  
Heliospheric Current Sheet ◽  
Particle Model ◽  
The Earth ◽  
Monitor Data ◽  
Mev Protons

<p>The influence of the heliospheric current sheet (HCS) on the propagation of high energy solar protons is explored using 3D test particle modelling. The test particle model, which includes drift effects, is used to simulate specific past ground level enhancement (GLE) events which cover a range of HCS configurations. For example, the effects of a source location close to and far from the HCS for events both poorly and well-connected to Earth are examined. Similarly, the effect of the Earth’s location relative to the HCS is explored. The modelling is performed for high energy (300-1200 MeV) protons to represent the energetic conditions under which GLEs occur. The derived intensity profiles at 1AU are compared to observations from HEPAD onboard GOES, as well as STEREO (at locations away from Earth) and neutron monitor data. </p>

Searching for 3D effects in the optical, high spectral resolution emission spectrum of KELT-9b

2021 ◽  
Author(s):  
Lorenzo Pino ◽  
Matteo Brogi ◽  
Jean-Michel Désert ◽  
Emily Rauscher
Keyword(s):  
Emission Spectrum ◽  
Spectral Resolution ◽  
Planet Formation ◽  
Emission Spectra ◽  
Optical Emission ◽  
High Spectral Resolution ◽  
Optical Emission Spectrum ◽  
Hot Jupiters ◽  
Atmospheric Structure ◽  
3D Effects

<p>Ultra-hot Jupiters (UHJs; T<sub>eq</sub> ≥ 2500 K) are the hottest gaseous giants known. They emerged as ideal laboratories to test theories of atmospheric structure and its link to planet formation. Indeed, because of their high temperatures, (1) they likely host atmospheres in chemical equilibrium and (2) clouds do not form in their day-side. Their continuum, which can be measured with space-facilities, can be mostly attributed to H- opacity, an indicator of metallicity. From the ground, the high spectral resolution emission spectra of UHJs contains thousands of lines of refractory (Fe, Ti, TiO, …) and volatile species (OH, CO, …), whose combined atmospheric abundances could track planet formation history in a unique way. In this talk, we take a deeper look to the optical emission spectrum of KELT-9b covering planetary phases 0.25 - 0.75 (i.e. between secondary eclipse and quadrature), and search for the effect of atmospheric dynamics and three-dimensionality of the planet atmosphere on the resolved line profiles, in the context of a consolidated statistical framework. We discuss the suitability of the traditionally adopted 1D models to interprete phase-resolved observations of ultra-hot Jupiters, and the potential of this kind of observations to probe their 3D atmospheric structure and dynamics. Ultimately, understanding which factors affect the line-shape in UHJs will also lead to more accurate and more precise abundance measurements, opening a new window on exoplanet formation and evolution.</p>

A new model describing Forbush Decreases at Mars: combining the heliospheric modulation and the atmospheric influence

2020 ◽  
Author(s):  
Jingnan Guo ◽  
Robert Wimmer-Schweingruber ◽  
Mateja Dumbovic ◽  
Bernd Heber ◽  
Yuming Wang
Keyword(s):  
Interplanetary Space ◽  
Atmospheric Transport ◽  
Forbush Decrease ◽  
Martian Atmosphere ◽  
Galactic Cosmic Rays ◽  
Interplanetary Coronal Mass Ejections ◽  
Forbush Decreases ◽  
Mars Atmosphere ◽  
Interaction Regions ◽  
Energy Dependent

<p>Forbush decreases are depressions in the galactic cosmic rays (GCRs) which are mostly caused by the modulations of interplanetary coronal mass ejections (ICMEs) and also sometimes by stream/corotating interaction regions (SIRs/CIRs). Forbush decreases have been studied extensively using neutron monitors at Earth and have been recently, for the first time, measured on the surface of another planet - Mars by the Radiation Assessment Detector (RAD), on board Mars Science Laboratory’s (MSL) rover Curiosity. The modulation of the GCR particles by heliospheric transients in space is energy-dependent and afterwards these particles are also interacting with the Martian atmosphere with the interaction process depending on the particle type and energy. In order to study the space weather environment near Mars using the ground-measured Forbush decreases, it is important to understand and quantify the energy-dependent modulation of the GCR particles by not only the pass-by heliospheric disturbances but also the Martian atmosphere. In this study, we develop a model which combines the heliospheric modulation of GCRs and the atmospheric modification of such modulated GCR spectra to quantify the amplitudes of the Forbush decreases at Mars: both on ground and in the interplanetary space near Mars during the pass-by of an ICME/SIR. The modeled results are in good agreement when compared to studies of Forbush decreases caused by ICMEs/SIRs measured by MSL on the surface of Mars and by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft in orbit.  This supports the validity of both the Forbush decrease description and the Martian atmospheric transport models.  Our model can be potentially used to understand the property of ICMEs and SIRs passing Mars.</p>

scholarly journals Deploying four optical UAV-based sensors over grassland: challenges and limitations

2015 ◽  
Vol 12 (1) ◽  
pp. 163-175 ◽  
Author(s):  
S. K. von Bueren ◽  
A. Burkart ◽  
A. Hueni ◽  
U. Rascher ◽  
M. P. Tuohy ◽  
...  
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Infrared Camera ◽  
Ground Level ◽  
Analysis Data ◽  
High Spectral Resolution ◽  
Spectral Measurements ◽  
Pasture Management ◽  
Vegetation Monitoring ◽  
Multispectral Camera

Abstract. Unmanned aerial vehicles (UAVs) equipped with lightweight spectral sensors facilitate non-destructive, near-real-time vegetation analysis. In order to guarantee robust scientific analysis, data acquisition protocols and processing methodologies need to be developed and new sensors must be compared with state-of-the-art instruments. Four different types of optical UAV-based sensors (RGB camera, converted near-infrared camera, six-band multispectral camera and high spectral resolution spectrometer) were deployed and compared in order to evaluate their applicability for vegetation monitoring with a focus on precision agricultural applications. Data were collected in New Zealand over ryegrass pastures of various conditions and compared to ground spectral measurements. The UAV STS spectrometer and the multispectral camera MCA6 (Multiple Camera Array) were found to deliver spectral data that can match the spectral measurements of an ASD at ground level when compared over all waypoints (UAV STS: R2=0.98; MCA6: R2=0.92). Variability was highest in the near-infrared bands for both sensors while the band multispectral camera also overestimated the green peak reflectance. Reflectance factors derived from the RGB (R2=0.63) and converted near-infrared (R2=0.65) cameras resulted in lower accordance with reference measurements. The UAV spectrometer system is capable of providing narrow-band information for crop and pasture management. The six-band multispectral camera has the potential to be deployed to target specific broad wavebands if shortcomings in radiometric limitations can be addressed. Large-scale imaging of pasture variability can be achieved by either using a true colour or a modified near-infrared camera. Data quality from UAV-based sensors can only be assured, if field protocols are followed and environmental conditions allow for stable platform behaviour and illumination.

scholarly journals From the Sun to Earth: effects of the 25 August 2018 geomagnetic storm

2020 ◽  
Vol 38 (3) ◽  
pp. 703-724 ◽  
Author(s):  
Mirko Piersanti ◽  
Paola De Michelis ◽  
Dario Del Moro ◽  
Roberta Tozzi ◽  
Michael Pezzopane ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Interplanetary Space ◽  
Current System ◽  
Ground Level ◽  
The Sun ◽  
Geomagnetically Induced Currents ◽  
Instrumental Approach ◽  
Sequence Of Events ◽  
Mass Ejection ◽  
European Sector

Abstract. On 25 August 2018 the interplanetary counterpart of the 20 August 2018 coronal mass ejection (CME) hit Earth, giving rise to a strong G3 geomagnetic storm. We present a description of the whole sequence of events from the Sun to the ground as well as a detailed analysis of the observed effects on Earth's environment by using a multi-instrumental approach. We studied the ICME (interplanetary-CME) propagation in interplanetary space up to the analysis of its effects in the magnetosphere, ionosphere and at ground level. To accomplish this task, we used ground- and space-collected data, including data from CSES (China Seismo-Electric Satellite), launched on 11 February 2018. We found a direct connection between the ICME impact point on the magnetopause and the pattern of Earth's auroral electrojets. Using the Tsyganenko TS04 model prevision, we were able to correctly identify the principal magnetospheric current system activating during the different phases of the geomagnetic storm. Moreover, we analysed the space weather effects associated with the 25 August 2018 solar event in terms of the evaluation of geomagnetically induced currents (GICs) and identification of possible GPS (Global Positioning System) losses of lock. We found that, despite the strong geomagnetic storm, no loss of lock had been detected. On the contrary, the GIC hazard was found to be potentially more dangerous than other past, more powerful solar events, such as the 2015 St Patrick's Day geomagnetic storm, especially at latitudes higher than 60∘ in the European sector.

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