Response Of Terrestrial And Martian Middle And Upper Atmosphere To Particle Precipitations

Energetic charged particles in interplanetary space and near-Earth space can affect the production and living environment of human beings through single-event effects and particle precipitations in the atmosphere.The precipitation of energetic particles can not only affect the ionosphere through processes such as ionization and dissociation;it can also change the physical and chemical properties of the neutral atmosphere through the interactions between a series of complex processes.In the thermosphere,particle precipitation will lead significant temperature increment through particle heating and Joule heating.However,the response of mesosphere to energetic particle precipitation is not very clear.And the scientists still not reach a consensus.The ratio of the energy depositions through dynamical and chemical processes caused by particle precipitation has no been understood clearly.In the solar system,Mars is the most similar the terrestrial planets to Earth.Through plenty of observation from artificial satellites,landers and rovers,Mars can be used as a natural experimental environment which is comparable to Earth.By study-ing the particle precipitations on Mars and Earth and compare the different responses of the atmospheres,we can further explore both the dynamic effects related to the magnetic field and the chemical effects related to changes in atmospheric compositions,to find the primary response of the atmosphere to energetic particle precipitations.This thesis contains two parts:the response of Earth's atmosphere to energetic particle precipita-tion;and the particle precipitation into Mars's atmosphere.The main works associated are as below:(1)Analysis of the general response of the mesospheric HO2 and O3 to large solar proton events.We used the proton flux data observed by GOES 13 and confirmed 7 large solar proton events that occurred from 2012 to 2017.Using the ionization rates data,we obtained the ionization production rate of the atmosphere and the expected changes in the compositions of the mesosphere.Then,by analysing the observations from Aura MLS,we verified that mesospheric HO2 increment and O3 depletion in the polar region during each solar proton event.Finally,by superimposing the responses of HO2 anf O3,we found that HO2 can increase by 1.0 ppbv above 0.2 hPa,and the peak always occurs at 0.1 hPa.O3 decreases within 0.02-1.0 hPa and lasts for as long as 7 days.The peak of the O3 can be more than 10%.The correlation analysis between HO2 and O3 proved that the increase of HO2 is the reason for the O3 depletion.(2)Simulation of the response of OH,HO2 and O3 to energetic particle precip-itations through WACCM model and the verification of the chemical mechanism of the atmospheric responses during energetic particle precipitation.Through comparative experiments by adding or removing the input of ionization productoin caused by energetic particle precipitations in WACCM,we found that the particle precipitations cause the chemical equilibrium shift through ionizing the atmo-sphere.In areas where both the ionization production rate and HOx density are high,HOx will increase during the energetic particle precipitations.Meanwhile,O3 depletion will occur due to the catalytic decomposition reactions involved by HOx.(3)First statistical result that found the upper mesospheric heating and the de-scent of the mesopause during energetic electron precipitation.We carried out a statistical study on the effects of strong geomagnetic activity on the mesopause over the auroral region from 2002 to 2018.When the auroral electro-jet index increased significantly(AE changes from<200 nT to>500 nT),the energetic electron precipitation from the POES MEPED was enhanced by several multiples of 10 for the 55-70° geomagnetic latitude band.The temperatures measured by the SABER instrument increased immediately in the mesopause region,together with a descent of the mesopause of about 0.5-2 km.Due to the depth that the precipitation can affect,we conclude that the mesopause is mainly influenced by electrons in the energy range 30-100 keV.The maximum temperature increment at 95 km can reach 4 K and the delay of the response can be up to 1 day.In general,we find that the temperatures significantly respond to the electron precipitation at as low as 93 km,within the mesopause region in most of a year.(4)Changes of the Martian neutral atmosphere and ionosphere during particle precipitations.Using the joint observations of SEP,SWEA,and NGIMS aboard MAVEN,we ana-lyzed the temperature of neutral atmosphere during particle precipitations and found no evident response.This result may relate to:the lack of a uniform region—like auroral zone on Earth—that particles precipitate on Mars;the amount of retrieved temperature data is not enough and the difficulty to show effective temperature changes during parti-cle precipitations;the temperature retrieval algorithm is still to be improved.Then,we analyzed the response of the Martian ionosphere to particle precipitations at night.In a single abundance profile below 200 km,there are some dependences between ion den-sities and the electron flux.Statistically,the dependences between CO2+ and O+which due to electron impact ionization is much stronger than that between O2+which due to fast ion chemical reactions.