English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Observations of continuous radio and sporadic X-ray emission from low-massobjects suggest they harbour localized plasmas in their atmosphericenvironments. For low-mass objects, the degree of thermal ionization isinsufficient to qualify the ionized component as a plasma, posing the question:what ionization processes can efficiently produce the required plasma that isthe source of the radiation? We propose Alfv\'{e}n ionization as a mechanismfor producing localized pockets of ionized gas in the atmosphere, havingsufficient degrees of ionization ($\geq10^{-7}$) that they constitute plasmas.We outline the criteria required for Alfv\'{e}n ionization and demonstrate it'sapplicability in the atmospheres of low-mass objects such as giant gas planets,brown dwarfs and M-dwarfs for both solar and sub-solar metallicities. We findthat Alfv\'{e}n ionization is most efficient at mid to low atmosphericpressures where a seed plasma is easier to magnetize and the pressure gradientsneeded to drive the required neutral flows are the smallest. For the modelatmospheres considered, our results show that degrees of ionization of$10^{-6}-1$ can be obtained as a result of Alfv\'{e}n ionization. Observableconsequences include continuum Bremsstrahlung emission, superimposed withspectral lines from the plasma ion species (e.g. He, Mg, H$_{2}$ or CO lines).Forbidden lines are also expected from the metastable population. The presenceof an atmospheric plasma opens the door to a multitude of plasma and chemicalprocesses not yet considered in current atmospheric models. The occurrence ofAlfv\'{e}n ionization may also be applicable to other astrophysicalenvironments such as protoplanetary disks.

Ionization in Atmospheres of Brown Dwarfs and Extrasolar Planets V: Alfv\'{e}n Ionization