The image below shows polar stratospheric clouds (or mother-of-pearl clouds) over Kiruna and has been taken in January 2007. It is thought that these clouds have some relationship with physical-chemical dynamics in the polar stratosphere.
What are the Sun-Earth interactions?
¶ What are the Sun-Earth interactions?
Nowadays we who get benefits from the highly electrified modern life should not ignore the Sun-Earth interactions. The following image shows the concept that how the Sun affects our modern life styles on the Earth.
The Sun-Earth interactions are usually discussed in terms of a short-term perspective, i.e. space weather. With respect to space weather, we concern about the Sun-Earth interactions in the time span of from a couple of days to a couple of years.
Our sun is about 5 billion years old and in a steady state in astronomy speaking. However, for us, not only the human beings but also all the creatures on the Earth, the Sun is not serene.
The Sun has a quasi-periodic 11-year cycle for its activity and during the most active phase (Solar Maximum) there are high probabilities that solar storms take place. The solar storms and the subsequent geomagnetic storms are the keys and important for space weather.
» For more read, Space Weather and it's Risks (PDF)
The above figure shows the medium-term space weather from another point of view, i.e. troposphere-upper atmosphere connection. In these days giant cumulonimbus clouds are often formed and thus 1) overshooting top can supply water vapour across the tropopause into the stratosphere, and 2) thunderstorms are formed more frequent.
The water vapour is transported both horizontally and vertically in the upper atmosphere and spreads to global. As the results, we get to observe often the upper atmospheric clouds such as nacreous clouds (or mother-of-pearl clouds) in the stratosphere and noctilucent clouds in the mesosphere.
Thunderstorm's lightning does not only direct downward but also upward. This upward-directiong electrical discharge is nowadays known as transient luminous events (TLE). Not much about the TLE is investigated but it is reported that the electric potential difference associated with the upward lightning can accelerate electrons to relativistic.
» More about upward-directing lightning over thunderstorm, Gigantic Jets Above Hurricane Hilda (@SpaceWeather.com)
» More about sprites from space, Sprites at the Eadge of Space (@SpaceWeather.com)
The Sun-Earth interactions, however, do not mean just solar-/geomagnetic storms. The Sun is constantly blowing solar wind consisting of plasmas (protons and electrons) and solar magnetic fields toward the interplanetary space. Namely that the solar winds constantly interact with the Earth's magnetosphere.
One of the visible/visual phenomena concerning the Sun-Earth interactions is aurorae.
The Sun-climate connection
...the luminosity of our own sun varies a measly 0.1% over the course of the 11-year solar cycle.
There is, however, a dawning realization among researchers that even these apparently tiny variations can have a significant effect on terrestrial climate. A new report (The Effects of Solar Variability on Earth's Climate) issued by the National Research Council (NRC) lays out some of the surprisingly complex ways that solar activity can make itself felt on our planet.
[Source: Solar variability and terrestrial climate, January 8, 2013, Science News@NASA]
The figure below shows the degree of invation of precipitating energetic particles into the polar upper atmosphere, i.e. stratosphere and mesosphere. The solar protons in the figure are directly emitted by the Sun mostly associated with solar flare, and usually get energised by solar flare and therefore these solar protons are called solar energetic particles (SEP). The SEP are less energetic compared to galactic cosmic rays (GCR) but nowadays it is considered that the impact onto the polar upper atmosphere due to the precipitating SEP cannot be ignored.
There are other precipitating energetic particles into the polar upper atmosphere: auroral electrons and electrons originated from the outer radiation belt (so-called the Van Allen radiation belt). The energies of auroral electrons range from 1 keV (kilo electronvolts) up to about 100 keV, while the energies of the radiation belt-originated electrons range from sub- to 1 MeV (mega electronvolts) up to about a couple of tens of MeV (and particularly electrons with more than 0.5 MeV are called relativistic). In addition to the precipitating SEP, these energetic electrons can also contribute to impact the polar upper atmosphere in the same manner as SEP does.
[Source: C. Jackman, The Impact of Energetic Particle Precipitation on the Atmosphere,The Effects of Solar Variability on Earth's Climate]
The figure below shows the Galactic Cosmic Rays (GCR)-atmosphere interactions in the lower atmosphere, i.e. troposphere. GCR have typically higher energies compared to the SEP, e.g. more than 1 GeV (giga electronvolts, 1000 times larger than 1 MeV), and thus can easily penetrate deeper into the atmosphere. Due to both EM (electromagnetic) and hadronic cascades, the radiation level is quite high. Meanwhile, the flux amount of GCR is suppressed and decreases when the interplanetary magnetic fields, i.e. solar magnetic fields, are strengthened. This phenomenon is called Forbush Decrease.
The data in the third row shows the ground-level neutrons (secondary cosmic-ray particles, see the figure above). When the count of neutrons goes below the zero-line (relative baseline), it is said that GCR are suffered Forbush Decrease.
» For more read, Primary Cosmic Rays (A compendium for Solar System Physics, PDF)
» For more read concerning the radiation level in the troposphere due to GCR, Rads (Radiations) on a plane (@SpaceWeather.com)
» For more read concerning the Pfotzer Maximum of GCR in the atmosphere, Cosmic rays in the atmosphere (@SpaceWeather.com)
[Personal Comment on the above article] There is a figure comparing the two flight profiles: one over California (geomagnetic latitude: 41.03°N for 35°N/120°W) and the other over New Hampshire (geomagnetic latitude: 53.49°N for 44°N/71°W). It is reasonable that the higher geomagnetic latitude is, the higher dose of radiation due to GCR is. This is because of the geomagnetic rigidness.
» For more read concerning the GCR detection by neutrons, Neutrons on a plane (@SpaceWeather.com)
[Personal Comment on the above article] It is good to read on the diffrent types of radiation (α, β, γ and neutrons) (@Wikipedia).
The latest works related to the Earth's climate in terms of the Sun-Earth interactions
NOx is a generic term for the mono-nitrogen oxides NO and NO2 (nitric oxide and nitrogen dioxide). They are produced from the reaction of nitrogen and oxygen gases in the air during, such as combustion and thunderstorm, especially at high temperatures.
In the same manner, NOx is produced by the impact of precipitating energetic particles into the polar upper atmosphere.
NOx in the upper atmosphere (i.e. stratosphere and mesosphere) is a long-lived chemical specie, easily subject to transported both horizontally and vertically, and readily reacts with ozone and destructs it.
» Also refer to: E. Turunen, Monitoring relativistic electron precipitation into atmosphere
¶ Overview of the latest works
Overview 1
The purpose of the terrestrial MeV space physics in the context is to investigate both spatial and temporal distributions of the relativistic electron precipitations (REP) in the polar upper atmosphere.
More precise and technically, we do not directly detect REP but generated gamma rays in the process of Bremsstrahlung ("deceleration radiation").
Overview 2
The SEP cannot easily access to any regions other than the polar regions due to the geomagnetic rigidness. Therefore the precipitating energetic particles, such as SEP and REP, impact onto the upper atmosphere takes place only in the polar region.
Overview 3
We have planned a circum-polar long-duration balloon campaign for the balloon-borne Electron Tracking Compton Camera (ETCC) (1, 2), developed by Professor Tanimori and his research group at Kyoto University in Japan.
The balloon-borne ETCC aims to detect galactic gamma-ray (in the figure, by "CN/GRB mode") and atmospheric gamma-ray (in the figure, by "REP mode"). The energies of these gamma rays range from sub- to several MeV (mega electronvolts).
Overview 4
The ETCC has been improved in terms of the capability of detecting line-gamma rays emitted by the excited atmospheric species (12C, 14N and 16O) being collided by the secondary neutrons (of 1-10 MeV and the primary particles are >10 MeV solar protons).
List of Works
1. SMILE-II: Observation of Celestial and Atmospheric MeV Gamma Rays using a Balloon-Borne Wide Feilds of View Electron Tracking Compton Camera, 2011, Proceedings of the ESA PAC-Symposium
2. Observation of MeV-Gamma-Rays from relativistic electron precipitation using a Electron Tracking Compton Camera with Balloon Borne Experiment, 2011, International Symposium of EISCAT (European Incoherent Scatter Scientific Association)
3. Planning of a circum-polar balloon flight campaigne for the Electron Tracking Compton Camera (ETCC), 2011, Poster Presentation at NorWiP (Nordic Women in Physics)
4. Development of electron tracking Compton camera for both balloon and future satellite experiments of MeV gamma-ray astronomy, 2012, GRB Meeting at Extreme Universe Laboratory, Russia
5. Improvement and current status of the ETCC, 2015, Presentation at STE (Solar-Terrestrial Environment Laboratory, Nagoya University)-ERG Workshop [Courtesy of Professor Tanimori]
6. An Electron-Tracking Compton Telescope for a Survey of the Deep Universe by MeV gamma-rays, 2015, accepted to the Astrophysical Journal [Courtesy of Professor Tanimori]
Miscellaneous
§ Profile of Sachiko Arvelius, Ph.D.
§ Doctoral Thesis: Energization and Acceleration of Dayside Polar Outflowing Oxygen [IRF Scientific Report 287, ISSN 0284-1703; ISBN 91-7305-963-3]