“Ionospheric Geography”

Bea Gallardo-Lacourt – UCLA 2016 Joint CEDAR-GEM Workshop – Santa Fe, NM - 06/19/2016 “Ionospheric Geography” Tutorial By Bea Gallardo-Lacourt What is the ? • The atmosphere above ~70km that is parally ionized by ultraviolet radiaon from the sun § This region of parally ionized gas extends upwards to high altudes where it merges with the • The ionosphere was discovered in the early 1900s in connecon with long distance radio transmissions • It affects all aspects of radio wave propagaon on • It’s an important (and very useful!!) tool in understanding how the sun affects the Earth’s environment Ionization of the atmosphere • Formaon of layers can be understood by considering ionizaon of any molecule (or atom) A in the atmosphere Rate of reacon depends on concentraon A+hν A++e- of molecules A and photons hν

• At high altudes there are Rate of electron Photon flux many photons, but few producon parcles • At low altudes there are Altude many parcles but few Parcle density photons of sufficient energy to cause ionizaon

Chapman Layers • Sydney Chapman used several assumpons to develop a simplified theorecal model ü Atmosphere consists of only one gas ü Radiaon from the sun is monochromac ü Atmospheric density decreases exponenally with height ü Solar radiaon is aenuated exponenally ü Earth is flat • Each atmospheric species has its own ionizaon potenal and reacon rate Ionosphere can be modeled as superposion of simple Chapman layers Chapman Layers • Sydney Chapman used several assumpons to develop a simplified theorecal model ü Atmosphere consists of only one gas ü Radiaon from the sun is monochromac ü Atmospheric density decreases exponenally with height ü Solar radiaon is aenuated exponenally ü Earth is flat • Each atmospheric species has its own ionizaon potenal and reacon rate Ionosphere can be modeled as superposion of simple Chapman layers Chapman Layers • Sydney Chapman used several assumpons to develop a simplified theorecal model ü Atmosphere consists of only one gas ü Radiaon from the sun is monochromac ü Atmospheric density decreases exponenally with height ü Solar radiaon is aenuated exponenally ü Earth is flat • Each atmospheric species has its own ionizaon potenal and reacon rate Ionosphere can be modeled as superposion of simple Chapman layers Ionization source: Solar radiation Ionization source: Solar radiation

Limitaons of Chapman Law

• Effects of magnec field • Collisions • Scale height is not constant • Assumes steady state - No other ionizaon sources - Constant intensity • Severely underesmate nighme D-region • Gives only quantave descripon Ionization source: particle precipitation (electrons) • In the auroral zone, also precipitang electrons and ions cause ionizaon • Much more variable than solar irradiance and thus much more difficult to model • Maintain ionosphere during the nighme o Before recombinaon, electrons scaer from the atmosphere and produce bremsstrahlung (x-ray)

~ 230 km Red color at 630 nm Electrons hing atomic Oxygen

~110 km Green color at 557.7 nm Electrons hing atomic Oxygen

~90 km Purple color at 427.8 nm Electrons hing Nitrogen molecules Ionization source: particle precipitation (protons) Proton • Weak blue emission at 486.1 nm (Hβ) and red emission at 656.3 nm (Hα) as different excitations of neutral hydrogen • Diffuse glow

Protons may make charge exchange with neutral hydrogen Ionospheric regions D region (70-90 km) • Lowest region, produced by Lyman series alpha radiaon (λ= 121.6 nm) ionizing Nitric Oxide (NO) • Very weakly ionized • Electron densies of 108 –1010 e-/m3 during the day • At night, when there is lile incident radiaon (except for cosmic rays), the D layer mostly disappears except at very high latudes

E Region (90-140 km) F1 Layer (140-200km) • Produced by X-ray and far ultraviolet • Electron density ~3x1011e-/m3

radiaon ionizing molecular oxygen (O2) • Caused by ionizaon of atomic Oxygen • Daylight maximum electron density of (O) by extreme ultraviolet radiaon about 1011e-/m3 (10-100nm) - Occurs at ~100km F2 Layer (>200km) • At night the E layer begins to disappear due • Usually has highest electron density to lack of incident radiaon (~2x1012e-/m3) - This results in the height of maximum • Consists primarily of ionized atomic density increasing Oxygen (O+) and Nitrogen (N+)

Ionospheric regions Ionospheric regions Latitudinal domains in the ionosphere: The ionosphere at high, middle and low latitudes High-Latude Ionosphere

Flow channel from the cap as a precursor of substorm onset [Nishimura et al., 2013]

• Polar cap patches are localized enhancements in ionospheric density. • Polar cap arcs are arcs propagang in the polar cap during periods of northward IMF • Poleward boundary intensificaons (PBI) are intensificaons along the poleward boundary of the auroral oval • Auroral stremers are roughly north-south aligned arcs that travels within the auroral oval High-Latude Ionosphere

Flow channel from the polar cap as a precursor of substorm onset [Nishimura et al., 2013]

Ionospheric phenomena at high-latude

ü Propagang plasma patches ü Cusp neutral fountain ü Neutral density structures ü Neutral wind ü Geomagnec storms ü Substorms ü Energec ion oulow

Low and mid-Latude Ionosphere

Ionospheric phenomena at low and mid- latude

ü Equatorial electroject ü Fountain effect ü Subauroral polarizaon streams (SAPS) ü South Atlanc anomalies ü Equatorial bubbles ü Tide and gravity waves ü Ionospheric storms ü Equatorial plasma instabilies ü Sporadic E layers ü Mid-latude plasma instabilies

Concluding remarks

The Ionosphere is amazingly interesting!!!!!

• The ionosphere is a partially ionized layer above 70km • Ionosphere shows solar activity dependence • Ionized by: Solar radiation and particle precipitation • The ionosphere has layers: D, E and F • The ionosphere has different latitudinal domains: polar cap, auroral zone, sub-auroral latitudes, mid-latitudes, low latitudes, equatorial zone) Many thanks to the organizers, specially Victoriya and Lindsay, for giving me the possibility to present this tutorial And many many thanks to Victor Pinto for helping me in downloading cool videos for the tutorial