RADIO STAR SCINTILLATIONS AND IONOSPHERIC DISTURBANCES

1959 ◽  
Vol 37 (10) ◽  
pp. 1137-1152 ◽  
Author(s):  
T. R. Hartz
Keyword(s):  
Geographical Location ◽  
Generation Mechanism ◽  
Upper Atmosphere ◽  
Ionospheric Disturbances ◽  
High Latitudes ◽  
General Belief ◽  
Auroral Activity ◽  
Middle Latitudes ◽  
Low Latitudes ◽  
Spread F

The generation mechanism for the ionization irregularities in the upper atmosphere which are responsible for radio star scintillations is considered. The general belief that scintillations are related to the spread-F phenomenon observed on ionosonde recordings is found to be an inadequate explanation for the scintillations at 53 Mc/s recorded at Ottawa. An examination of the Ottawa recordings shows that there is a definite association, both in time of occurrence and geographical location, with those ionospheric disturbances that are usually considered to be due to incoming solar particles. Since other workers at more southerly geomagnetic latitudes have associated their scintillation observations with the spread-F phenomenon which they consider to be independent of auroral activity, it would appear that two mechanisms, at least, are responsible for the radio star fluctuations: namely, the precipitation of solar corpuscles and a mechanism linked with the spread-F phenomenon. The former seems to predominate at high latitudes, the latter is probably predominant at low latitudes, while both mechanisms probably are operative in middle latitudes.

scholarly journals On the observed changes in upper stratospheric and mesospheric temperatures from UARS HALOE

2008 ◽  
Vol 26 (5) ◽  
pp. 1287-1297 ◽  
Author(s):  
E. Remsberg
Keyword(s):  
Time Series ◽  
Solar Cycle ◽  
Linear Regression ◽  
Linear Trend ◽  
Upper Atmosphere ◽  
Middle Latitudes ◽  
Solar Occultation ◽  
Decadal Scale ◽  
Low Latitudes ◽  
Pressure Altitude

Abstract. Temperature versus pressure or T(p) time series from the Halogen Occultation Experiment (HALOE) of the Upper Atmosphere Research Satellite (UARS) have been extended and re-analyzed for the period of 1991–2005 and for the upper stratosphere and mesosphere in 10-degree wide latitude zones from 60 S to 60 N. Even though sampling from a solar occultation experiment is somewhat limited, it is shown to be quite adequate for developing both the seasonal and longer-term variations in T(p). Multiple linear regression (MLR) techniques were used in the re-analyses for the seasonal and the significant interannual, solar cycle (SC-like or decadal-scale), and linear trend terms. Plots of the amplitudes and phases for the interannual (QBO and subbiennial) terms are provided. A simple SC-like term of 11-yr period was fitted to the time series residuals after accounting for the seasonal and interannual terms. Highly significant SC-like responses were found for both the upper mesosphere and the upper stratosphere. The phases of these SC-like terms were checked for their continuity with latitude and pressure-altitude; the larger amplitude responses are directly in-phase with that of standard proxies for the solar flux variations. The analyzed, max minus min, responses at low latitudes are of order 0.5 to 1 K, while at middle latitudes they are as large as 3 K in the upper mesosphere. Highly significant, linear cooling trends were found at middle latitudes of the middle to upper mesosphere (−1.5 to −2.0 K/decade), at tropical latitudes of the lower mesosphere (about −0.5 K/decade), and at 2 hPa (of order −1 K/decade). Both the diagnosed solar cycle responses and trends from HALOE for the mid to upper mesosphere at middle latitudes are larger than simulated with most models, perhaps an indication of decadal-scale dynamical forcings that are not being simulated so well.

scholarly journals The impact of CMEs on the critical frequency of F2-layer ionosphere (foF2)

2019 ◽  
Vol 15 (S356) ◽  
pp. 400-402
Author(s):  
Alene Seyoum ◽  
Nat Gopalswamy ◽  
Melessew Nigussie ◽  
Nigusse Mezgebe
Keyword(s):  
Critical Frequency ◽  
Angular Width ◽  
High Latitudes ◽  
Solar Cycles ◽  
Middle Latitudes ◽  
Low Latitudes ◽  
Critical Frequency Fof2 ◽  
The Impact ◽  
Very High

AbstractThe ionospheric critical frequency (foF2) from ionosonde measurements at geographic high, middle, and low latitudes are analyzed with the occurrence of coronal mass ejections (CMEs) in long term variability of the solar cycles. We observed trends of monthly maximum foF2 values and monthly averaged values of CME parameters such as speed, angular width, mass, and kinetic energy with respect to time. The impact of CMEs on foF2 is very high at high latitudes and low at low latitudes. The time series for monthly maximum foF2 and monthly-averaged CME speed are moderately correlated at high and middle latitudes.

scholarly journals Iodine chemistry in the chemistry–climate model SOCOL-AERv2-I

2021 ◽  
Vol 14 (10) ◽  
pp. 6623-6645
Author(s):  
Arseniy Karagodin-Doyennel ◽  
Eugene Rozanov ◽  
Timofei Sukhodolov ◽  
Tatiana Egorova ◽  
Alfonso Saiz-Lopez ◽  
...  
Keyword(s):  
Lower Stratosphere ◽  
Climate Model ◽  
Geographical Location ◽  
Lower Troposphere ◽  
Fold Increase ◽  
High Latitudes ◽  
Iodine Species ◽  
Low Latitudes ◽  
Iodine Chemistry ◽  
Ozone Column

Abstract. In this paper, we present a new version of the chemistry–climate model SOCOL-AERv2 supplemented by an iodine chemistry module. We perform three 20-year ensemble experiments to assess the validity of the modeled iodine and to quantify the effects of iodine on ozone. The iodine distributions obtained with SOCOL-AERv2-I agree well with AMAX-DOAS observations and with CAM-chem model simulations. For the present-day atmosphere, the model suggests that the iodine-induced chemistry leads to a 3 %–4 % reduction in the ozone column, which is greatest at high latitudes. The model indicates the strongest influence of iodine in the lower stratosphere with 30 ppbv less ozone at low latitudes and up to 100 ppbv less at high latitudes. In the troposphere, the account of the iodine chemistry reduces the tropospheric ozone concentration by 5 %–10 % depending on geographical location. In the lower troposphere, 75 % of the modeled ozone reduction originates from inorganic sources of iodine, 25 % from organic sources of iodine. At 50 hPa, the results show that the impacts of iodine from both sources are comparable. Finally, we determine the sensitivity of ozone to iodine by applying a 2-fold increase in iodine emissions, as it might be representative for iodine by the end of this century. This reduces the ozone column globally by an additional 1.5 %–2.5 %. Our results demonstrate the sensitivity of atmospheric ozone to iodine chemistry for present and future conditions, but uncertainties remain high due to the paucity of observational data of iodine species.

scholarly journals Ionospheric <i>fo</i>F2 anomalies during some intense geomagnetic storms

2005 ◽  
Vol 23 (7) ◽  
pp. 2487-2499 ◽  
Author(s):  
R. P. Kane
Keyword(s):  
Geomagnetic Storms ◽  
Early Morning ◽  
Equatorial Ionosphere ◽  
Storm Event ◽  
Ionospheric Disturbances ◽  
High Latitudes ◽  
Negative Effects ◽  
Local Effects ◽  
Positive Effects ◽  
Low Latitudes

Abstract. The global evolutions of foF2 anomalies were examined for three very intense geomagnetic storms, namely the Halloween events of October-November 2003 (Event X, 29–30 October 2003, Dst –401 nT; Event Y, 20–21 November 2003, Dst –472 nT), and the largest Dst storm (Event Z, 13–14 March 1989, Dst –589 nT). For Event X, troughs (negative storms) were clearly seen for high northern and southern latitudes. For northern midlatitudes as well as for low latitudes, there were very strong positive effects on 29 October 2003, followed by negative effects the next day. For Event Y, there were no troughs in NH high latitudes for morning and evening hours but there were troughs for night. For midlatitudes and low latitudes, some longitudes showed strong negative effects in the early morning as expected, but some longitudes showed strong positive effects at noon and in the evening hours. Thus, there were many deviations from the model patterns. The deviations were erratic, indicating considerable local effects superposed on general patterns. A disconcerting feature was the presence of strong positive effects during the 24 h before the storm commencement. Such a feature appears only in the 24 h before the geomagnetic storm commencement but not earlier. If genuine, these could imply a prediction potential with a 24-h antecedence. For Event Z (13–14 March 1989, equinox), all stations (all latitudes and longitudes) showed a very strong "negative storm" in the main phase, and no positive storms anywhere. Keywords. Ionosphere (Equatorial ionosphere – Ionospheric disturbances – Mid-latitude Ionosphere – Polar ionosphere)

scholarly journals Iodine chemistry in the chemistry-climate model SOCOL-AERv2-iodine

2021 ◽  
Author(s):  
Arseniy Karagodin-Doyennel ◽  
Eugene Rozanov ◽  
Timofei Sukhodolov ◽  
Tatiana Egorova ◽  
Alfonso Saiz-Lopez ◽  
...  
Keyword(s):  
Climate Model ◽  
Geographical Location ◽  
Lower Troposphere ◽  
Fold Increase ◽  
High Latitudes ◽  
Ozone Loss ◽  
Low Latitudes ◽  
Iodine Chemistry ◽  
Ozone Column ◽  
Good Agreement

Abstract. This paper introduces a new version of the chemistry-climate model SOCOL-AERv2, supplemented by an iodine chemistry module. We conducted three twenty-year-long ensemble experiments to assess the validity of modeled iodine and to quantify the effects of iodine on ozone. The obtained iodine distributions with SOCOL-AERv2-iodine show good agreement with the CAM-chem model simulations and AMAX-DOAS observations. For the present-day atmosphere, the model suggests the strongest influence of iodine in the lower stratosphere with an ozone loss of up to 30 ppbv at low latitudes and up to 100 ppbv at high latitudes. Globally averaged, the model suggests iodine-induced chemistry to result in an ozone column reduction of 3–4 %, maximizing at high latitudes. In the troposphere, iodine chemistry lowers tropospheric ozone concentrations by 5–10 % depending on the geographical location. We also determined the sensitivity of ozone to iodine applying a 2-fold increase of iodine emissions, which reduces the ozone column globally by an additional 1.5–2.5 %. We found that in the lower troposphere, the share of ozone loss induced by iodine originating from inorganic sources is 75 % and 25 % by iodine originating from organic sources, and contributions become similar at about 50 hPa. These results constrain the importance of atmospheric iodine chemistry for present and future conditions, even though uncertainties remain high due to the paucity of observational data of iodine species.

The paleomagnetism of Huronian red beds and Nipissing diabase; Post-Huronian Igneous Events and apparent polar path for the interval −2300 to −1500 Ma for Laurentia

1976 ◽  
Vol 13 (6) ◽  
pp. 749-773 ◽  
Author(s):  
J. L. Roy ◽  
P. L. Lapointe
Keyword(s):  
High Stability ◽  
Vertical Axis ◽  
Time Range ◽  
High Latitudes ◽  
Red Beds ◽  
Two Stage ◽  
Low Latitudes ◽  
The Many ◽  
Age Determinations ◽  
Good Agreement

Thermal, chemical, and alternating field (and two-stage) cleaning treatments of Huronian sediments and Nipissing diabase (which intrudes the sediments) from the Cobalt area yield five directions of magnetizations (A–E) of high stability; A, B, C, and E are found in the sediments, and C, D, and E in the diabase. It is suggested that magnetization B (337°, +52°; α95 = 8°; pole 158 °E, 67 °N) was acquired shortly after deposition of the Firstbrook beds [Formula: see text]; magnetization C (259°, +82°; α95 = 5°; pole 258 °E, 42 °N), found in both the diabase and sediments in contact with the diabase, was acquired during cooling following emplacement of the diabase [Formula: see text]; and magnetizations D and E, yielding poles at 264 °E, 15 °S and 000°, 09 °N respectively, were produced during the Hudsonian orogeny (−1850 to −1700 Ma). This interpretation resolves the previous inconsistencies between poles and age determinations. Good agreement between results from the Nipissing diabase and other igneous bodies indicate that widespread igneous events occurred in the time range approximately −2200 to −2100 Ma, immediately following deposition of Huronian sediments. This is referred to as 'Post-Huronian Igneous Events'. A proposed apparent polar path relative to Laurentia shows two distinct motions; for the 2300–1850 Ma interval, a latitudinal change (roughly along longitude 250° E) from high [Formula: see text] to low [Formula: see text] latitudes and, for the 1850–1500 Ma interval, a displacement along the present-day equator with first an eastward motion to about 000° longitude followed by a westward motion to 240° E longitude; the apex of the eastward excursion is given a date of [Formula: see text]. It is possible that this reflects a rotation of Laurentia about a vertical axis at the time of and following the Hudsonian orogeny. Subsequent uplift and cooling would explain the many overprinted stable magnetizations yielding poles distributed along the equator (track 4). Latitude maps indicate that Laurentia was in high latitudes from 2200–2000 Ma and in intermediate to low latitudes from 1900–1500 Ma.

scholarly journals The Influence of Ocean Thermocline Temperatures on the Earth’s Surface Climate

2005 ◽  
Vol 18 (13) ◽  
pp. 2222-2246 ◽  
Author(s):  
Robert J. Oglesby ◽  
Monica Y. Stephens ◽  
Barry Saltzman
Keyword(s):  
Carbon Dioxide ◽  
Mixed Layer ◽  
General Circulation ◽  
Atmospheric Carbon Dioxide ◽  
Deep Ocean ◽  
High Latitudes ◽  
Surface Climate ◽  
Low Latitudes ◽  
Atmospheric Carbon ◽  
The Impact

Abstract A coupled mixed layer–atmospheric general circulation model has been used to evaluate the impact of ocean thermocline temperatures (and by proxy those of the deep ocean) on the surface climate of the earth. Particular attention has been devoted to temperature regimes both warmer and cooler than at present. The mixed layer ocean model (MLOM) simulates vertical dynamics and thermodynamics in the upper ocean, including wind mixing and buoyancy effects, and has been coupled to the NCAR Community Climate Model (CCM3). Simulations were made with globally uniform thermocline warmings of +2°, +5°, and +10°C, as well as a globally uniform cooling of −5°C. A simulation was made with latitudinally varying changes in thermocline temperature such that the warming at mid- and high latitudes is much larger than at low latitudes. In all simulations, the response of surface temperature over both land and ocean was larger than that expected just as a result of the imposed thermocline temperature change, largely because of water vapor feedbacks. In this respect, the simulations were similar to those in which only changes in atmospheric carbon dioxide were imposed. In fact, when carbon dioxide was explicitly changed along with thermocline temperatures, the results were not much different than if only the thermocline temperatures were altered. Land versus ocean differences are explained largely by latent heat flux differences: the ocean is an infinite evaporative source, while land can be quite dry. The latitudinally varying case has a much larger response at mid- to high latitudes than at low latitudes; the high latitudes actually appear to effectively warm the low latitudes. Simulations exploring scenarios of glacial inception suggest that the deep ocean alone is not likely to be a key trigger but must operate in conjunction with other forcings, such as reduced carbon dioxide. Moist upland regions at mid- and high latitudes, and land regions adjacent to perennial sea ice, are the preferred locations for glacial inception in these runs. Finally, the model combination equilibrates very rapidly, meaning that a large number of simulations can be made for a fairly modest computational cost. A drawback to this is greatly reduced sensitivity to parameters such as atmospheric carbon dioxide, which requires a full response of the ocean. Thus, this approach can be considered intermediate between fixing, or prescribing, sea surface temperatures and a fully coupled modeling approach.

scholarly journals Interannual variability of precipitable water

1996 ◽  
Vol 14 (4) ◽  
pp. 464-467 ◽  
Author(s):  
R. P. Kane
Keyword(s):  
Interannual Variability ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Precipitable Water ◽  
Radiosonde Data ◽  
High Latitudes ◽  
Zonal Winds ◽  
Low Latitudes ◽  
Linear Trends

Abstract. The 12-month running means of the surface-to-500 mb precipitable water obtained from analysis of radiosonde data at seven selected locations showed three types of variability viz: (1) quasi-biennial oscillations; these were different in nature at different latitudes and also different from the QBO of the stratospheric tropical zonal winds; (2) decadal effects; these were prominent at middle and high latitudes and (3) linear trends; these were prominent at low latitudes, up trends in the Northern Hemisphere and downtrends in the Southern Hemisphere.

Sign in / Sign up

Export Citation Format

Share Document