Pfotzer Maximum Research Articles

The Atmospheric Influence on Cosmic-Ray-Induced Ionization and Absorbed Dose Rates

When high-energy particles originating from space penetrate the atmosphere, they may interact with atoms and molecules, initiating air showers composed of secondary and tertiary particles propagating towards the ground. They can cause ionization of the atmosphere and contribute to the radiation dose at low altitudes. This work uses the GEANT-4-based Atmospheric Radiation Interaction Simulator (AtRIS) toolkit to compute these quantities in the Earth’s atmosphere. We take advantage of the unique Planet Specification File (PSF) of the Atmospheric Radiation Interaction Simulator (AtRIS) to investigate the effect of the state of the atmosphere on the resulting induced ionization and absorbed dose rates from the top of the atmosphere (at 100 km) down to the surface. The atmospheric profiles (density, pressure, temperature, and composition) are computed with the NRLMSISE-00 model at various latitudes and for every month of 2014, corresponding to the last maximum of solar activity. The resulting ionization and dose rates present different profiles that vary with latitude in the atmosphere, with the relative difference between equatorial and high latitude ionization rates reaching 68% in the Pfotzer maximum. We obtain differences of up to 59% between the equator and high latitudes observed at commercial flight altitudes for the radiation dose. Both ionization and absorbed dose rates also feature anti-phased seasonal variations in the two hemispheres throughout 2014. Based on these results, we computed global maps of the ionization and dose rates at fixed altitudes in the atmosphere by using precomputed maps of the effective vertical cutoff rigidities and the results of three AtRIS simulations to consider the effect of latitude. While sharing the same general structure as maps created with a single profile, these new maps also show a clear asymmetry in the ionization and absorbed dose rates in the polar regions.

Application of CORSIMA (Cosmic Ray Spectrum and Intensity in Middle Atmosphere) Model for Solar Cosmic Rays. Case Study of the Extremes GLE 05 and GLE 69

The new model CORSIMA (COsmic Ray Spectrum and Intensity in Middle Atmosphere) is presented. The spectra and intensities of solar cosmic rays (SCR) from GLE (Ground Level Enhancement) 05 on 23 February 1956 and GLE 69 on 20 January 2005 at different altitudes are calculated. For this purpose, the operational CORSIMA model is applied. In the final version of the CORSIMA program, an approximation in 6 characteristic energy intervals of the Bohr–Bethe–Bloch function is used, including the charge decrease interval. Analytical expressions for the contributions of the energy intervals are provided.
 For the first time we present a quantitative and qualitative appreciation of the impact of Solar Cosmic Rays (SCRs) from the Solar Particle Events (SPEs) on the ionosphere and middle atmosphere (30–80 km). These altitudes are above the Regener–Pfotzer maximum.
 Unlike Galactic Cosmic Rays (GCR), the differential spectra of SCR essentially vary in time. The SCR fluxes also differ from each other during the different events. The spectrum and intensity behaviour is explained considering the structure of the CORSIMA program. The calculation results are in agreement with the experimental data and show characteristic features of the propagation process for different altitudes and geomagnetic latitudes. The calculations are performed for geomagnetic latitudes 90° (cusp region). The development of this research is important for the processes and mechanisms of space weather.

Cosmic Ray Spectrum and Intensity in Middle Atmosphere (CORSIMA) model. Use and Application for Solar Cosmic Rays

The new model CORSIMA (COsmic Ray Spectrum and Intensity in Middle Atmosphere) is presented. The spectra and intensities of solar cosmic rays (SCR) from GLE (Ground Level Enhancement) 05 on 23 February 1956 and GLE 69 on 20 January 2005 at different altitudes are calculated. For this purpose, the operational CORSIMA model is applied. In the final version of the CORSIMA program, an approximation in 6 characteristic energy intervals of the Bohr-Bethe-Bloch function is used, including the charge decrease interval. Analytical expressions for the contributions of the energy intervals are provided. For the first time we present a quantitative and qualitative appreciation of the impact of Solar Cosmic Rays (SCRs) from the Solar Particle Events (SPEs) on the ionosphere and middle atmosphere (30 - 80 km). These altitudes are above the Regener – Pfotzer maximum. Unlike Galactic Cosmic Rays (GCR), the differential spectra of SCR essentially vary in time. The SCR fluxes also differ from each other during the different events. The spectrum and intensity behavior is explained considering the structure of the CORSIMA program. The calculation results are in agreement with the experimental data and show characteristic features of the propagation process for different altitudes and geomagnetic latitudes. The calculations are performed for geomagnetic latitudes 90o (cusp region). The development of this research is important for the processes and mechanisms of space weather.

Improved Cosmic Ray Spectrum and Intensity in Middle Atmosphere (CORSIMA) Model Considering Six Characteristic Energy Intervals


 
 
 The new model CORSIMA (COsmic Ray Spectrum and Intensity in Mid- dle Atmosphere) is presented in this study. Numerical determinations of the spectrum and intensity of Galactic Cosmic Rays (GCR) for the middle atmo- sphere and the lower altitudes of the ionosphere (30–80 km) are presented. These altitudes are above the Regener–Pfotzer maximum. The primary spec- tra of protons and helium (alpha particles) are used. According to the amount of particles, cosmic rays consist of 92% protons, 6% helium nuclei, 1% heavier elements, and 1% electrons (GINZBURG and SIROVATSKY [19]).
 We also use the approximation of ionization losses (Bohr–Bethe–Bloch formula) in six characteristic energy intervals, including the charge decrease interval for electron capture. In this way, the accuracy of the obtained results is improved.
 Analytical expressions for the contributions of the energy intervals are provided. An approximation of the ionization function on six energy intervals is used and the charge decrease interval for electron capture is studied. Numerical calculations are performed using computational algebra systems.
 The development of this research is important for a better understanding of the processes and mechanisms of space weather. The GCR affect the ionization and electrical parameters in the atmosphere and also the chemical processes (ozone formation and depletion in the stratosphere) in it. These effects can be significantly enhanced during strong and moderately strong solar proton events and geomagnetic storms.
 
 

MEASUREMENT OF THE REGENER-PFOTZER MAXIMUM USING DIFFERENT TYPES OF IONISING RADIATION DETECTORS AND A NEW TELEMETRY SYSTEM TF-ATMON.

Stratospheric balloons are a useful tool for the investigation of cosmic radiation at high altitudes and the tests of new detectors of cosmic radiation. Due to necessary data processing, the balloon gondola needs to carry, together with radiation detectors, additional supplementary sensors measuring humidity, temperature, location and orientation, altitude, atmospheric pressure, acceleration, etc. A newly developed universal system TF-ATMON, based on using already existing tools of the PX4 open-source project, enables apart from data recording and monitoring, also the possibility to trace the balloon gondola after the flight. The application was demonstrated on stratospheric balloon flight FIK-6. This flight was unique because three different types of radiation detectors were used at one flight. It enabled us to compare the altitude of the Regener-Pfotzer maximum measured with different types of sensors sensitive to a different type of secondary cosmic radiation generated in the atmosphere.

The North-West University’s High Altitude Radiation Monitor programme

Since the discovery of cosmic radiation by Victor Hess in 1912, when he reported a significant increase in radiation as altitude increases, concerns about radiation effects on human bodies and equipment have grown over the years. The secondary and tertiary particles which result from the interaction of primary cosmic rays with atmospheric particles and commercial aircraft components, are the primary cause of the radiation dose deposited in human bodies and in electronic equipment (avionics) during aircraft flights. At an altitude of about 10 km (or higher) above sea level, the dose received by frequent flyers, and especially flight crew, is a serious concern. Also of concern is the possible failure of sensitive equipment on board commercial aircrafts as a result of flying through this mixed radiation field. Monitoring radiation in the atmosphere is therefore very important. Here we report on the first measurements by the High Altitude Radiation Monitor (HARM) detector during a commercial flight from Johannesburg (O.R. Tambo International Airport) to Windhoek (Hosea Kutako International Airport). As part of a public awareness activity, the HARM detector was placed on a high-altitude balloon, and these measurements are also shown here. Model calculations (estimations) of radiation levels for the commercial aircraft flight are shown and the results are used to interpret our measurements.
 Significance:
 
 Measurements of the Regener–Pfotzer maximum in South Africa and dosimetric measurements on board a commercial flight are presented.
 These radiation measurements are compared to model calculations which can be used to predict the radiation dose during commercial flights.
 This study also aims to raise public awareness about the atmospheric radiation environment from ground level to the Regener–Pfotzer peak at high altitude.

Near-space operation of compact CsI, CLYC, and CeBr[formula omitted] sensors: Results from two high-altitude balloon flights

Three different types of gamma-ray sensors (CsI, CLYC, and CeBr3) were flown on balloon flights as hosted payloads. Two CsI sensors were flown from a September 2014 flight from Fort Sumner, New Mexico for 18 h; CLYC and CeBr3 sensors were flown from Antarctica in December 2016 for 22 days. The data from these flights were used to test and characterize the operation of these sensors in a near-space environment. All sensors returned excellent data. Gamma rays, neutrons, and energetic galactic cosmic rays (GCRs) were measured. Expected atmospheric features, such as the Regener–Pfotzer maximum, were observed, and gamma-ray line emission from materials near the sensors, as well as atmospheric oxygen and nitrogen, were detected. The measured data were compared to simulations of energetic protons, neutrons, and 0.511 MeV gamma rays produced by GCR interactions with the atmosphere. While the simulated protons and neutrons generally matched the data, there were fewer simulated 0.511 MeV gamma rays than measured with the data. This mismatch is likely due to additional 0.511 MeV gamma rays produced in material near the sensors that were not taken into account in the simulations. Discussion is provided for how these types of measurements in space-based missions can be used to characterize upper atmospheric densities at planets with dense atmospheres like the Earth.

CARI-7A: DEVELOPMENT AND VALIDATION.

Aircrew members can be exposed to higher annual doses of natural ionizing radiation than members of the general population in most parts of the world. The principal ionizing radiation to which they are exposed is galactic cosmic radiation (GCR). Among the particles present in the primary spectrum are heavy ions: relativistic nuclei of lithium and heavier elements. These ions have very high radiation weighting factors and can contribute significantly to the effective dose at altitudes above the Pfotzer maximum. This report describes the latest version of the US Federal Aviation Administration's GCR flight dose calculation software, CARI-7A. Unlike its predecessor, CARI-6, CARI-7A directly includes heavy ion transport, using a database of atmospheric particle spectra generated by incident GCR ions pre-calculated with MCNPX 2.7.0. to enable calculations to the edge of space. Results are compared with measurements aboard commercial passenger aircraft, high altitude research aircraft and similar calculations by others.

Cosmic radiation dose measurements from the RaD-X flight campaign

Abstract The NASA Radiation Dosimetry Experiment (RaD-X) stratospheric balloon flight mission obtained measurements for improving the understanding of cosmic radiation transport in the atmosphere and human exposure to this ionizing radiation field in the aircraft environment. The value of dosimetric measurements from the balloon platform is that they can be used to characterize cosmic ray primaries, the ultimate source of aviation radiation exposure. In addition, radiation detectors were flown to assess their potential application to long-term, continuous monitoring of the aircraft radiation environment. The RaD-X balloon was successfully launched from Fort Sumner, New Mexico (34.5°N, 104.2°W) on 25 September 2015. Over 18 hours of flight data were obtained from each of the four different science instruments at altitudes above 20 km. The RaD-X balloon flight was supplemented by contemporaneous aircraft measurements. Flight-averaged dosimetric quantities are reported at seven altitudes to provide benchmark measurements for improving aviation radiation models. The altitude range of the flight data extends from commercial aircraft altitudes to above the Pfotzer maximum where the dosimetric quantities are influenced by cosmic ray primaries. The RaD-X balloon flight observed an absence of the Pfotzer maximum in the measurements of dose equivalent rate.

Assessment of the influence of the RaD-X balloon payload on the onboard radiation detectors

The NASA Radiation Dosimetry Experiment (RaD-X) stratospheric balloon flight mission, launched on 25 September 2015, provided dosimetric measurements above the Pfotzer maximum. The goal of taking these measurements is to improve aviation radiation models by providing a characterization of cosmic ray primaries, which are the source of radiation exposure at aviation altitudes. The RaD-X science payload consists of four instruments. The main science instrument is a tissue-equivalent proportional counter (TEPC). The other instruments consisted of three solid state silicon dosimeters: Liulin, Teledyne total ionizing dose (TID) and RaySure detectors. The instruments were housed in an aluminum structure protected by a foam cover. The structure partially shielded the detectors from cosmic rays but also created secondary particles, modifying the ambient radiation environment observed by the instruments. Therefore, it is necessary to account for the influence of the payload structure on the measured doses. In this paper, we present the results of modeling the effect of the balloon payload on the radiation detector measurements using a Geant-4 (GEometry ANd Tracking) application. Payload structure correction factors derived for the TEPC, Liulin, and TID instruments are provided as a function of altitude. Overall, the payload corrections are no more than a 7% effect on the radiation environment measurements.

Bi-decadal solar influence on climate, mediated by near tropopause ozone

The Sun's contribution to climate variations was highly questioned recently. In this paper we show that bi-decadal variability of solar magnetic field, modulating the intensity of galactic cosmic ray (GCR) at the outer boundary of heliosphere, could be easily tracked down to the Earth's surface. The mediator of this influence is the lower stratospheric ozone, while the mechanism of signal translation consists of: (i) GCR impact on the lower stratospheric ozone balance; (ii) modulation of temperature and humidity near the tropopause by the ozone variations; (iii) increase or decrease of the greenhouse effect, depending on the sign of the humidity changes. The efficiency of such a mechanism depends critically on the level of maximum secondary ionisation created by GCR (i.e. the Pfotzer maximum) – determined in turn by heterogeneous Earth's magnetic field. Thus, the positioning of the Pfotzer max in the driest lowermost stratosphere favours autocatalytic ozone production in the extra-tropical Northern Hemisphere (NH), while in the SH– no suitable conditions for activation of this mechanism exist. Consequently, the geomagnetic modulation of precipitating energetic particles – heterogeneously distributed over the globe – is imprinted on the relation between ozone and humidity in the lower stratosphere (LS). The applied test for causality reveals that during the examined period 1957–2012 there are two main centres of action in the winter NH, with tight and almost stationary winter ozone control on the near tropopause humidity. Being indirectly influenced by the solar protons, the variability of the SH lower stratospheric ozone, however, is much weaker. As a consequence, the causality test detects that the ozone dominates in the interplay with ULTS humidity only in the summer extra-tropics.

Monte Carlo simulations of the secondary neutron ambient and effective dose equivalent rates from surface to suborbital altitudes and low Earth orbit

Occupational exposures from ionizing radiation are currently regulated for airline travel (<20 km) and for missions to low-Earth orbit (∼300–400 km). Aircrew typically receive between 1 and 6 mSv of occupational dose annually, while aboard the International Space Station, the area radiation dose equivalent measured over just 168 days was 106 mSv at solar minimum conditions. It is anticipated that space tourism vehicles will reach suborbital altitudes of approximately 100 km and, therefore, the annual occupational dose to flight crew during repeated transits is expected to fall somewhere between those observed for aircrew and astronauts. Unfortunately, measurements of the radiation environment at the high altitudes reached by suborbital vehicles are sparse, and modelling efforts have been similarly limited. In this paper, preliminary MCNPX radiation transport code simulations are developed of the secondary neutron flux profile in air from surface altitudes up to low Earth orbit at solar minimum conditions and excluding the effects of spacecraft shielding. These secondary neutrons are produced by galactic cosmic radiation interacting with Earth's atmosphere and are among the sources of radiation that can pose a health risk. Associated estimates of the operational neutron ambient dose equivalent, used for radiation protection purposes, and the neutron effective dose equivalent that is typically used for estimates of stochastic health risks, are provided in air. Simulations show that the neutron radiation dose rates received at suborbital altitudes are comparable to those experienced by aircrew flying at 7 to 14 km. We also show that the total neutron dose rate tails off beyond the Pfotzer maximum on ascension from surface up to low Earth orbit.

Erich Regener and the ionisation maximum of the atmosphere

Abstract. In the 1930s the German physicist Erich Regener (1881–1955) did important work on the measurement of the rate of production of ionisation deep under water and in the atmosphere. Along with one of his students, Georg Pfotzer, he discovered the altitude at which the production of ionisation in the atmosphere reaches a maximum, often, but misleadingly, called the Pfotzer maximum. Regener was one of the first to estimate the energy density of cosmic rays, an estimate that was used by Baade and Zwicky to bolster their postulate that supernovae might be their source. Yet Regener's name is less recognised by present-day cosmic ray physicists than it should be, largely because in 1937 he was forced to take early retirement by the National Socialists as his wife had Jewish ancestors. In this paper we briefly review his work on cosmic rays and recommend an alternative naming of the ionisation maximum. The influence that Regener had on the field through his son, his son-in-law, his grandsons and his students, and through his links with Rutherford's group in Cambridge, is discussed in an appendix. Regener was nominated for the Nobel Prize in Physics by Schrödinger in 1938. He died in 1955 at the age of 73.

Study of properties of cosmic rays and solar X-ray flares by balloon borne experiments

We are engaged in pioneering balloon borne experiments with typical payloads less than ~3.5 kg. Low cost rubber balloons are used to fly them to a height of about 40 km. In a double balloon system, the booster balloon lifts the orbiter balloon to its cruising altitude where data is taken for a longer period of time. In this paper, we present our first scientific report on the variation of cosmic rays and muons with altitude and detection of several solar flares in X-rays between 20 and 100 keV. We have found the altitude of the Pfotzer maximum at Tropic of Cancer for cosmic rays and muons and catch several solar flares in hard X-rays. We find that the hard X-ray (>40 keV) sky becomes very transparent above Pfotzer maximum. We find the flare spectrum to have a power-law distribution. From these studies, we infer that valuable scientific research could be carried out in near space using low cost balloon borne experiments.

Radioactivity in the atmosphere over Hong Kong

Upper-air radioactivity soundings have been regularly conducted in Hong Kong since 1994. A total of 38 soundings, measuring the vertical profile of radioactivity in the atmosphere over Hong Kong using on-board Geiger-Müeller tubes, were made during the period 1994–2003 in different seasons and weather conditions. This paper presents the data obtained in Hong Kong and compares the composite vertical profile with observations in other parts of the world. The average Pfotzer maximum over Hong Kong was found to be at an altitude of around 16.1 km, lower than those observed at higher latitudes. The variations of the Pfotzer maximum with geomagnetic rigidity and solar activity are discussed. Seasonal and local weather effects on radioactivity in the lower atmosphere were also studied.

Atmospheric X-rays at 11°S geomagnetic latitude

X-ray measurements at balloon altitudes were made at São José dos Campos, Brasil (23°12′S, 45°51′W geographic coordinates, ~11°S geomagnetic latitude) on 18 December 1981, using an omnidirectional NaI(T1) scintillation detector. Atmospheric X-rays, namely secondary X-radiation from cosmic rays, were measured for the energy interval 30–155 keV and up to an atmospheric depth of 5.5 g cm −2. A comparison of the flux measured at the Pfotzer maximum during these measurements with those obtained previously by several research groups at other latitudes and with a similar technique has also been made. Finally, a comparison of the atmospheric component with that attributed to the diffuse component is also presented and it is concluded that both components are of about the same magnitude at ~ 5 g cm −2 and at ~ 11°S geomagnetic latitude.

Atmospheric gamma ray angle and energy distributions from sea level to 3.5 g/cm² and 2 to 25 MeV

Angle and energy distributions are reported here for gamma rays from ground level to 3.5 g/cm² residual atmosphere at energies of 2 to 25 MeV and zenith angles of 0° to 50° and 180° to 130°. They complement the previous results of Ryan et al. (1977) for altitudes above 100 g/cm². The observations were made with the University of California, Riverside (UCR), double Compton scatter telescope from a balloon launched from Palestine, Texas, geomagnetic cut‐off of 4.5 GV, on May 13, 1975. The ground level measurements were made at Riverside, California, at 1000‐g/cm² residual atmosphere, geomagnetic cut‐off of 5.4 GV, on July 21, 1977. Growth curves for downward‐moving gamma rays have pronounced maxima at 160±30 g/cm² residual atmosphere, while those for upward‐moving gamma rays are essentially constant at altitudes above the Pfotzer maximum. Below about 300 g/cm² both the downward and the upward fluxes decrease with average e‐folding depths of 192±15 and 179±12 g/cm², respectively. The ratio of the downward‐ to upward‐moving gamma rays near the vertical is 17±5, independent of depth below the Pfotzer maximum. The energy variation, E−1.1, of the downward‐moving gamma rays is flatter than the E−1.8 of the upward moving ones at all depths below 100 g/cm². All zenith angle distributions show peaks toward the horizon. Above the Pfotzer maximum the downward flux decreases more rapidly away from the horizon than the upward flux, while below the converse is true. The azimuth angle distributions at 4.0 g/cm² show northward anisotropies that increase with energy from 3.9±0.9% at 2–10 MeV to 7.0±2.3% at 10–25 MeV.

Energy spectrum and flux of fast neutrons in the atomsphere

The energy spectrum of fast neutrons (5-20 MeV) in the atmosphere at the Pfotzer maximum (\ensuremath{\sim} 100 ${\mathrm{g}/\mathrm{c}\mathrm{m}}^{2}$) was measured at geomagnetic latitude 42\ifmmode^\circ\else\textdegree\fi{}N (${P}_{c}=4.4$ GeV). The $n$-$\ensuremath{\gamma}$ detector was a 4.6 \ifmmode\times\else\texttimes\fi{} 4.65-cm cylindrical cell of organic liquid scintillator (NE213) coupled to a high-resolution, two-parameter, multiparticle pulse-shape discriminator with a two-parameter (64 \ifmmode\times\else\texttimes\fi{} 64) logarithmic pulse-height analyzer. An anticoincidence charged-particle shield completely enclosed the $n$-$\ensuremath{\gamma}$ detector. The spectral parameter $\ensuremath{\beta}(E)$ of the differential neutron energy spectrum decreased from 4.4 \ifmmode\pm\else\textpm\fi{} 0.8 in the range 3.5-6.0 MeV to 1.5 \ifmmode\pm\else\textpm\fi{} 1.0 in the range 11-20 MeV. The integrated neutron flux at Pfotzer maximum between 3.5 and 10.0 MeV was 0.36 \ifmmode\pm\else\textpm\fi{} 0.10 ${\mathrm{n}\mathrm{e}\mathrm{u}\mathrm{t}\mathrm{r}\mathrm{o}\mathrm{n}\mathrm{s}/\mathrm{c}\mathrm{m}}^{2}$ sec. The implications of these results for the high-energy albedo neutron leakage as a source of the energetic proton flux in the radiation belts are discussed.

Gamma rays and high-energy neutrons in the atmosphere

In continuation of our earlier experiments studying the emission of solar neutrons, we have now developed detector systems which respond to γ rays of energy 1–5 MeV and neutrons of energy [Formula: see text]. The two detectors are almost identical. Each consists of a CsI (Na) crystal (B) of diameter 3.8 cm, completely enclosed in a tapered cylinder of plastic scintillator (A) operated in anticoincidence; the crystals have thicknesses of 2.4 and 1.2 cm respectively. A balloon carrying these detectors was flown on March 16, 1967 over Hyderabad, India (vertical cutoff rigidity 16.9 GV) and floated at a ceiling altitude of 6.0 mb for 1 hour. In addition to γ-ray and neutron events (AB), events A and AB were also continuously monitored throughout the flight. Pulses corresponding to 1–5 MeV in the 2.4-cm crystal (γ rays) and 6–40 MeV in the 1.2-cm crystal (high-energy neutrons) were analyzed by a 64-channel pulse-height analyzer. On the basis of the pulse-height distributions and γ-ray efficiencies in the two crystals, we attribute events of 1–5 MeV energy from the thicker crystal to γ rays and those &gt; 10 MeV in energy from the thinner one to stars produced by high-energy neutrons [Formula: see text] in the crystal. Atmospheric growth curves for γ rays and neutrons have been obtained; these growth curves as well as those for events A and AB show the normal features of the Pfotzer maximum, steady decreases up to the ceiling altitude, and a constant counting rate at ceiling. The atmospheric counting rates at ceiling altitude give for γ rays of energy 1–5 MeV a flux of ~1 photon per cm2 s and for neutrons of energy [Formula: see text] a flux of ~0.1 neutron per cm2 s. No evidence for a solar component in either channel was found.

Cosmic ray balloon measurements at low geomagnetic latitudes, September 1962 through March 1964

In a series of high-altitude cosmic ray intensity measurements, the technique of constant level flights with small extensible balloons was used. A reliable valve-controlled system to level neoprene balloons with payloads of several kilograms at atmospheric depths between 4 and 10 g/cm2 was developed. The detector system consisted of a double coincidence GM counter telescope unit with telemetry of single counting rates, coincidence rate, atmospheric pressure, and internal temperature. Total payload weight was only 1500 grams. Thirty-seven balloon flights were made during the last two years to study the cosmic ray intensity at high altitudes and low altitudes. A computing method was developed to fit a function of the type C (x, pλ) = A exp (−x/L) - B exp (−x/l) to the counting rate versus atmospheric depth curve for each flight. This fit turned out to be excellent, leading to comprehensive information on the cosmic ray absorption, condensed into only three cutoff dependent parameters A, B, and L, and a constant parameter l. L represents the absorption length of the ionizing component; its mean value at 11.4-gv geomagnetic cutoff rigidity was found to be 158 g/cm2. The parameter l, representing the apparent mean collision length, has a value of 86 g/cm2. This method provides a statistically accurate way to determine the extrapolated counting rate at the top of the atmosphere, given by the difference Co = A - B. The correlation of the calculated counting rates at Pfotzer maximum and at the top of the atmosphere with the Mina Aguilar neutron monitor rate is analyzed for a period of 18 months of decreasing solar activity. A gradual softening of the primary spectrum during the eleven-year cycle recovery is revealed.