Now showing items 1-10 of 44
The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets
(Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-18)
This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other ...
Energy conversion in cometary atmospheres - Hybrid modeling of 67P/Churyumov-Gerasimenko
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-21)
<i>Aims</i>: We wish to investigate the energy conversion between particles and electromagnetic fields and determine the location where it occurs in the plasma environment of comets.<p> <p><i>Methods</i>: We used a hybrid plasma model that included photoionization, and we considered two cases of the solar extreme ultraviolet flux. Other parameters corresponded to the conditions of comet ...
First wind shear observation in PMSE with the tristatic EISCAT VHF radar
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-11-05)
The Polar Summer Mesosphere has the lowest temperatures that occur in the entire Earth system. Water ice particles below the optically observable size range participate there in the formation of strong radar echoes (Polar Mesospheric Summer Echoes, PMSE). To study PMSE we carried out observations with the European Incoherent Scatter (EISCAT) VHF and EISCAT UHF radar simultaneously from a site near ...
Temperature and thermal emission of cosmic dust in the vicinity of the Sun, Vega and Fomalhaut.
(Conference object; Konferansebidrag, 2018)
Dynamics of nanodust particles emitted from elongated initial orbits
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018)
<p><i>Context</i>: Because of high charge-to-mass ratio, the nanodust dynamics near the Sun is determined by interplay between the gravity and the electromagnetic forces. Depending on the point where it was created, a nanodust particle can either be trapped in a non-Keplerian orbit, or escape away from the Sun, reaching large velocity. The main source of nanodust is collisional fragmentation of ...
Dynamics of Dust Particles near Sun, Vega and Fomalhaut
(Conference object; Konferansebidrag, 2018)
Dust trajectory simulations around Sun, Vega, and Fomalhaut
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-20)
<p><i>Context - </i>Vega and Fomalhaut display a thermal emission brightness that can possibly arise from hot dust near the stars, an inner extension of their planetary debris disks. There was brought up an idea that nm-sized dust particles are kept in the vicinity of the stars by electromagnetic forces. This resembles the trapping that model calculations show in the corotating magnetic field in the ...
Radar studies of ionospheric dusty plasma phenomena
(Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-17)
We discuss the influence of charged dust on radar observations in the Earth ionosphere. This region in the upper Earth atmosphere can be described as a partially ionized, low‐temperature plasma. Plasma parameters vary by orders of magnitude spatially and in time. Dust particles influence the charge balance, in some cases dusty plasma condition is met. The polar mesospheric echoes are an example of ...
Dust sputtering within the inner heliosphere: a modelling study
(Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-03)
The aim of this study is to investigate how sputtering by impacting solar wind particles influence the lifetime of dust particles in the inner heliosphere near the Sun.<p><p> We consider three typical dust materials: silicate, Fe<sub>0.4</sub>Mg<sub>0.6</sub>O and carbon and describe their sputtering yields based on atomic yields given by the Stopping and Range of Ions in Matter (SRIM) package. ...
A comparison of contact charging and impact ionization in low-velocity impacts: implications for dust detection in space
(Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-15)
We investigate the generation of charge due to collision between projectiles with sizes below ∼1 µm and metal surfaces at speeds ∼0.1 to 10 km s−1. This corresponds to speeds above the elastic limit and well below speeds where volume ionization can occur. Impact charge production at these low to intermediate speeds has traditionally been described by invoking the theory of shock wave ionization. By ...